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Synthesis of pyrrolidines

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A new efficient method for the N-heterocyclization of primary amines with diols catalyzed by a Cp*Ir complex was developed. A variety of five-, six-, and seven-membered cyclic amines were synthesized in good to excellent yields.
K.-I. Fujita, T. Fujii, R. Yamaguchi, Org. Lett., 2004, 6, 3525-3528.


An acid-promoted synthesis of azaheterocycles from N-carbamate-protected amino alcohols involves the activation of the hydroxyl group via the use of orthoesters. Despite the reduced nucleophilicity of carbamate nitrogen, this reaction system provides several types of pyrrolidines and piperidines in very good yields.
H. Park, Y. Kwon, J. E. Shin, W.-J. Kim, S. Hwang, S. Lee, S. Kim, Synthesis, 2017, 49, 2761-2767.


A simple, one-pot preparation of cyclic amines via efficient chlorination of amino alcohols with use of SOCl2 obviates the need for the classical N-protection/O-activation/cyclization/deprotection sequence commonly employed for this type of transformation. The reaction pathways and the general scope of this method have also been investigated.
F. Xu, B. Simmons, R. A. Reamer, E. Corley, J. Murry, D. Tschaen, J. Org. Chem., 2008, 73, 312-315.


Using 0.5 mol % [Ru(p-cymene)Cl2]2 with the bidentate phosphines dppf or DPEphos as the catalyst, primary amines have been converted into secondary amines, and secondary amines into tertiary amines. N-Heterocyclization reactions of primary amines have been achieved, as well as alkylation reactions of primary sulfonamides.
M. H. S. A. Hamid, C. L. Allen, G. W. Lamb, A. C. Maxwell, H. C. Maytum, A. J. A. Watson, J. M. J. Williams, J. Am. Chem. Soc., 2009, 131, 1766-1774.


A one-pot synthesis of nitrogen-containing heterocycles from alkyl dihalides and primary amines and hydrazines occurs under microwave irradiation via a simple and efficient cyclocondensation in an alkaline aqueous medium.
Y. Ju, R. S. Varma, J. Org. Chem., 2006, 71, 135-141.


Dirhodium-catalyzed intramolecular nitrene insertion into sp3 C-H bonds enables a regio- and diastereoselective synthesis of N-unprotected pyrrolidines at rt without external oxidants, nitrene stabilizing groups, or directing functionality.
S. Munnuri, A. M. Adebesin, M. P. Paudyal, M. Yousufuddin, A. Dalipe, J. R. Falck, J. Am. Chem. Soc., 2017, 139, 18288-18294.


A copper-catalyzed intermolecular carboamination of potassium N-carbamoyl-β-aminoethyltrifluoroborates with terminal, 1,2-disubstituted, and 1,1-disubstituted vinylarenes bearing a number of functional groups provides 2-arylpyrrolidines. 1,3-Dienes are also good substrates, and their reactions give 2-vinylpyrrolidines.
C. Um, S. R. Chemler, Org. Lett., 2016, 18, 2515-2518.


A novel gold-catalyzed tandem cycloisomerization/hydrogenation of chiral homopropargyl sulfonamides provides various enantioenriched pyrrolidines in excellent yields and excellent enantioselectivities.
Y.-F. Yu, C. Shu, T.-D. Tan, L. Li, S. Rafique, L.-W. Ye, Org. Lett., 2016, 18, 5178-5181.


The use of Et3SiH and a catalytic amount of I2 enables transition-metal-free, intramolecular hydroalkoxylation/reduction and hydroamination/reduction of unactivated alkynes at room temperature to provide 2,4- and 2,5-disubstituted pyrrolidines as well as a 2,3-disubstituted tetrahydrofurans with high diastereoselectivity.
S. Fujita, M. Shibuya, Y. Yamamoto, Synthesis, 2017, 49, 4199-4204.


A metal-free method for a direct anti-Markovnikov hydroamination of unsaturated amines is enabled by irradiation of the amine substrates with visible light in the presence of catalytic quantities of easily synthesized 9-mesityl-10-methylacridinium tetrafluoroborate and thiophenol as a hydrogen-atom donor. The reaction furnished nitrogen-containing heterocycles with complete regiocontrol.
T. M. Nguyen, D. A. Nicewicz, J. Am. Chem. Soc., 2013, 135, 9588-9591.


The combination of chiral bicyclo[3.3.0]octadiene ligands, an active rhodium hydroxide complex, and neutral reaction conditions enabled a highly enantioselective rhodium-catalyzed arylation of aliphatic N-tosylaldimines in high yield. The application of this method is demonstrated by the enantioselective synthesis of chiral 2-aryl pyrrolidines and piperidines in a one-pot procedure.
Z. Cui, H.-J. Yu, F.-F. Yang, W.-Y. Gao, C.-G. Feng, G.-Q. Lin, J. Am. Chem. Soc., 2011, 133, 12394-12397.


Regioselective protonolytic C-C bond cleavage of acylated aminomethyl cyclopropanes can be achieved using trifluoroacetic acid to provide 2,2-substituted pyrrolidines via an intermediate tertiary carbenium ion. The strength of the acid and the amine substituent are important factors to achieve high regioselectivity, suggesting intramolecular proton transfer from the protonated amide function.
M. Skvorcova, A. Jirgensons, Org. Lett., 2017, 19, 2478-2481.


N-Iodosuccinimide promotes an attractive and productive protocol for the position-selective intramolecular C-H amination of aliphatic groups (Hofmann-Löffler reaction) employing sulfonimides as nitrogen sources initiated by visible light. The overall transformation provides pyrrolidines under mild and selective conditions as demonstrated for 17 different substrates.
C. Q. O'Broin, P. Fernández, C. Martínez, Kilian Muñiz, Org. Lett., 2016, 18, 436-439.


Efficient Ti-catalyzed radical formal [3+2] cycloadditions of N-acylaziridines and alkenes provide pyrrolidines from readily available starting materials. The overall redox-neutral reaction was achieved via a redox-relay mechanism, which harnesses radical intermediates for selective C-N bond cleavage and formation.
W. Hao, X. Wu, J. Z. Sun, J. C. Siu, S. N. MacMillan, S. Lin, J. Am. Chem. Soc., 2017, 139, 12141-12144.


The union of vinyl sulfones with photoredox-generated α-amino radicals enables direct C-H vinylations of N-aryl tertiary amines, as well as decarboxylative vinylations of N-Boc α-amino acids, to provide allylic amines of broad diversity in high yield and with excellent olefin geometry control. The utility of this reaction has been demonstrated via the syntheses of several natural products and a number of established pharmacophores.
A. Noble, D. W. C. MacMillan, J. Am. Chem. Soc., 2014, 136, 11602-11605.


A highly enantioselective iridium-catalyzed hydrogenation of cyclic enamines is efficient method for the synthesis of optically active cyclic tertiary amines including natural product crispine A.
G.-H. Hou, J.-H. Xie, P.-C. Yan, Q.-L. Zhou, J. Am. Chem. Soc., 2009, 131, 1366-1367.


A ruthenium catalyzed, atom-economical domino redox isomerization/cyclization of easily available, linear aminopropargyl alcohols provides added-value nitrogen heterocycles in a single catalytic step and displays a broad scope and functional group tolerance.
B. M. Trost, N. Maulide, R. C. Livingston, J. Am. Chem. Soc., 2008, 130, 16502-16503.


Optically pure C2-symmetrical cyclic amines were efficiently synthesized from the corresponding diols obtained from an enantioselective borohydride reduction of diketones in the presence of a chiral β-ketoiminato cobalt(II) catalyst.
M. Sato, Y. Gunji, T. Ikeno, T. Yamada, Synthesis, 2004, 1434-1438.


A cationic manganese porphyrin catalyst enables a formal [3+2] cycloaddition between aziridines and styrenes to give the corresponding pyrrolidines.
T. Ozawa, T. Kurahashi, S. Matsubara, Synlett, 2013, 24, 2763-2767.


Mild, rhodium-catalyzed hydroaminations of unactivated olefins with primary and secondary alkylamines form the corresponding five- and six-membered products in excellent yields. A variety of functional groups such as hydroxyl, halo, cyano, and carboalkoxyl groups were tolerated.
Z. Liu, J. F. Hartwig, J. Am. Chem. Soc., 2008, 130, 1570-1571.


[Ir(COD)Cl]2 is an effective precatalyst for the intramolecular hydroamination of a range of unactivated alkenes with pendant secondary amines. The catalyst can be used at relatively low loadings and without the need for added ligands or other cocatalysts.
K. D. Hesp, M. Stradiotto, Org. Lett., 2009, 11, 1449-1452.


A mild, effective gold(I)-catalyzed hydroamination of unactivated olefins to form protected nitrogen heterocycles has been developed. The substrate scope is broader than in reactions realized with late-transition-metal catalyst systems.
X. Han, R. A. Widenhoefer, Angew. Chem. Int. Ed., 2006, 45, 1747-1749.


Treatment of an N-4-pentenyl or N-5-hexenyl urea with a catalytic 1:1 mixture of a gold(I) N,N-diaryl imidazol-2-ylidine complex and AgOTf gave the corresponding nitrogen heterocycle in excellent yield via an intramolecular exo-hydroamination.
C. F. Bender, R. A. Widenhoefer, Org. Lett., 2006, 8, 5303-5305.


Homogeneous carboamination, carboalkoxylation and carbolactonization of terminal alkenes are realized via oxidative gold catalysis, providing expedient access to various substituted N- or O-heterocycles. Deuterium-labeling studies established the nature of the alkene functionalization and the indispensible role of Au(I)/Au(III) catalysis.
G. Zhang, L. Cui, Y. Wang, L. Zhang, J. Am. Chem. Soc., 2010, 132, 1474-1475.


The combination of carbaboranylmercuric chloride as a bulky Lewis acid and silver triflate efficiently catalyzes a cycloisomerization of 1,3-dienes at room temperature to give allyl-substituted azacycles and cycloalkanes in excellent yields with very high regioselectivity.
H. Yamamoto, I. Sasaki, S. Shiomi, N. Yamasaki, H. Imagawa, Org. Lett., 2012, 14, 2250-2253.


A catalyst composed of Pd(OAc)2 and S-Phos allows the conversion of aryl chlorides as electrophiles in Pd-catalyzed alkene carboamination and carboetherification, minimizes N-arylation, and prevents formation of regiosisomieric mixtures. Various heterocycles, including pyrrolidines, isoxazolidines, tetrahydrofurans, and pyrazolidines, are efficiently generated with this method.
B. R. Rosen, J. E. Ney, J. P. Wolfe, J. Org. Chem., 2010, 75, 2756-2759.


The stereoselective synthesis of N-acyl- and N-Boc-protected pyrrolidines via Pd-catalyzed reactions of γ-(N-acylamino) alkenes and γ-(N-Boc-amino) alkenes with aryl bromides proceeds with generally high levels of diastereoselectivity by formation of two bonds in a single operation.
M. B. Bertrand, J. P. Wolfe, Tetrahedron, 2005, 61, 6447-6459.


A mild and facile Pd-catalyzed intramolecular hydroamination of unactivated alkenes takes place at room temperature and tolerates acid-sensitive functional groups. The tridentate ligand on Pd effectively inhibits β-hydride elimination, thus the formation of hydroamination products is preferred over oxidative amination products.
F. E. Michael, B. M. Cochran, J. Am. Chem. Soc., 2006, 128, 4246-4247.


The gold(I)-catalyzed reaction of methylenecyclopropanes with sulfonamides produces the corresponding pyrrolidine derivatives in moderate to good yields via a domino ring-opening ring-closing hydroamination process.
M. Shi, L.-P. Liu, J. Tang, Org. Lett., 2006, 8, 4043-4046.


A simple iron-catalyzed intramolecular hydroamination of unactivated olefins proceeds under mild conditions and tolerates aminoolefins containing halide moieties.
K. Komeyama, T. Morimoto, K. Takaki, Angew. Chem. Int. Ed., 2006, 45, 2938-2941.


An unstabilized azomethine ylide generated from commercial trimethylamine N-oxide undergoes a remarkable 1,3-dipolar cycloaddition with electron-rich and unpolarized olefins to give challenging 3,4-di­substituted pyrrolidines in good yield. A broad range of substituents on the alkenes are tolerated provided they are compatible with excess LDA.
J. E. Davoren, D. L. Gray, A. R. Harris, D. M. Nason, W. Xu, Synlett, 2010, 2490-2492.


Organoselenium catalysis enables an efficient synthesis of oxygen and nitrogen heterocycles via exo-cyclization under mild conditions in the presence of 1-fluoropyridinium triflate. The reaction offers good functional group tolerance and excellent regioselectivity.
R. Guo, J. Huang, H. Huang, X. Zhao, Org. Lett., 2016, 18, 504-507.


A Pd-catalyzed reaction of vinyl iodides and N-tosylhydrazones assembles η3-allyl ligands through carbene insertion. Intramolecular trapping with nitrogen nucleophiles generates good yields of cinnamyl and pentadienyl amines like those found in alkaloid natural products.
A. Khanna, C. Maung, K. R. Johnson, T. T. Luong, D. L. Van Vranken, Org. Lett., 2012, 14, 3233-3235.


Enantioselective intramolecular oxidative amidation of alkenes has been achieved using a (pyrox)Pd(II)(TFA)2 as catalyst and O2 as the stoichiometric oxidant. The reactions proceed at room temperature in very good yields and with high enantioselectivity. Catalyst-controlled stereoselective cyclization reactions are demonstrated for a number of chiral substrates.
R. I. McDonald, P. W. White, A. B. Weinstein, C. P. Tam, S. S. Stahl, Org. Lett., 2011, 13, 2830-2833.


An asymmetric intramolecular hydroamination of allenes catalyzed by phosphinegold(I)-bis-p-nitrobenzoate complexes is applicable to the enantioselective formation of vinyl pyrrolidines and piperidines in high ee.
R. L. LaLonde, B. D. Sherry, E. J. Kang, F. D. Toste, J. Am. Chem. Soc., 2007, 129, 2452-2453.


Palladium-catalyzed intramolecular amination of unactivated C-H bonds at the γ and δ positions of picolinamide (PA) protected amine substrates enables the synthesis of azetidine, pyrrolidine, and indoline compounds. The method features relatively low catalyst loading, use of inexpensive reagents, convenient operating conditions and predictable selectivities.
G. He, Y. Zhao, S. Zhang, C. Lu, G. Chen, J. Am. Chem. Soc., 2012, 134, 3-6.


A wide variety of mixed anhydrides formed in situ from carboxylic acids and acyl chlorides can subsequently undergo metal insertion-decarboxylation-recombination to provide ketones in very good yield when subjected to metallaphotoredox catalysis. A three-step synthesis of the medicinal agent edivoxetine is also described.
C. Le, D. W. C. MacMillan, J. Am. Chem. Soc., 2015, 137, 11938-11941.


In the presence of MgI2 as Lewis acid, donor-acceptor cyclopropanes or corresponding cyclobutanes react with 1,3,5-triazinanes, leading to the 2-unsubstituted pyrrolidines and piperidines under mild conditions in good yields. This protocol tolerates various functional groups and provides an efficient entry to pyrrolidines and piperidines.
L. K. B. Garve, A. Kreft, P. G. Jones, D. B. Werz, J. Org. Chem., 2017, 82, 9235-9242.


Hoveyda-Grubbs catalyst in combination with BF3·OEt2 efficiently promotes tandem cross metathesis intramolecular aza-Michael reaction between enones and unsaturated carbamates resulting in the creation of β-amino carbonyl units. The use of microwave irradiation dramatically accelerates the process, but also inverts the stereoselectivity in the addition process.
S. Fustero, D. Jiménez, M. Sánchez-Roselló, C. del Pozo, J. Am. Chem. Soc., 2007, 129, 6700-6701.


1,3-Dipolar cycloaddition of in situ generated azomethine ylides to electron deficient olefins catalyzed by tris(pentafluorophenyl)borane is described.
P. Srihari, S. R. Yaragorla, D. Basu, S. Chandrasekhar, Synthesis, 2006, 2646-2648.


The Au(I)-catalyzed intramolecular hydroamination of N-allenyl carbamates was effective for the formation of various cyclic amines. γ-Hydroxy and δ-hydroxy allenes underwent Au-catalyzed intramolecular hydroalkoxylation to form the corresponding oxygen heterocycles in good yield. 2-Allenyl indoles underwent Au-catalyzed intramolecular hydroarylation to form 4-vinyl tetrahydrocarbazoles in good yield.
Z. Zhang, C. Liu, R. E. Kinder, X. Han, H. Qian, R. A. Widenhoefer, J. Am. Chem. Soc., 2006, 128, 9066-9073.


Under selected conditions, the Zr-catalyzed reaction of EtMgCl with imines produces C,N-dimagnesiated compounds, which can be further trapped with electrophiles. The overall transformation provides a new route to bifunctional or cyclic nitrogen-containing compounds such as 1-azaspirocyclic γ-lactams, pyrrolidines and azetidines.
V. Gandon, P. Bertus, J. Szymoniak, Synthesis, 2002, 1115-1120.


Ph3PAuOTf catalyzes efficient intra- and intermolecular hydroamination of unactivated olefins with sulfonamides.
J. Zhang, C.-G. Yang, C. He, J. Am. Chem. Soc., 2006, 128, 1798-1799.


An efficient alkene aza-Cope-Mannich cyclization between 2-hydroxy homoallyl tosylamine and aldehydes in the presence of iron(III) salts gives 3-alkyl-1-tosyl pyrrolidines in good yields via a γ-unsaturated iminium ion, 2-azonia-[3,3]-sigmatropic rearrangement, and intramolecular Mannich reaction. The cyclization of 2-hydroxy homopropargyl tosylamines gives dihydro-1H-pyrroles.
R. M. Carballo, M. Purino, M. A. Ramírez, V. S. Martín, J. I. Padrón, Org. Lett., 2010, 12, 5334-5337.


Bisphosphine-catalyzed mixed double-Michael reactions between amino-acid-derived pronucleophiles as Michael donors and electron-deficient acetylenes as acceptors afford β-amino carbonyl derivatives of oxazolidines, thiozolidines, and pyrrolidines in excellent yields and with high diastereoselectivities under operationally simple and mild conditions.
V. Sriramurthy, G. A. Barcan, O. Kwon, J. Am. Chem. Soc., 2007, 129, 12928-12929.


In the presence of 1.1 equiv of (Diacetoxyiodo)benzene (PIDA) and suitable halogen sources, a variety of olefins underwent haloamidation, haloetherification, and halolactonization to the corresponding 1,2-bifunctional cyclic skeletons in very good isolated yields. Subsequent mild nucleophilic substitution gives key intermediates for biologically interesting compounds in high yields.
G.-Q. Liu, Y.-M. Li, J. Org. Chem., 2014, 79, 10094-10109.


Iodocyclization of unsaturated tosylamides promoted by Oxone oxidation of KI afforded, in good yields, N-tosyl iodopyrrolidines and piperidines. A new, simple method for the conversion of alcohols to tosylamides is presented.
M. C. Marcotullio, V. Campagna, S. Sternativo, F. Costantino, M. Curini, Synthesis, 2006, 2760-2766.


The aza-Payne rearrangement of 2,3-aziridin-1-ols under basic conditions gives epoxy amines. Subsequent nucleophilic attack of the epoxide by dimethylsulfoxonium methylide yields a bis-anion, which upon a 5-exo-tet ring-closure yields the desired pyrrolidine. This process takes place with complete transfer of stereochemical fidelity and can be applied to sterically hindered aziridinols.
J. M. Schomaker, S. Bhattacharjee, J. Yan, B. Borhan, J. Am. Chem. Soc., 2007, 129, 1996-2003.


J. M. Schomaker, S. Bhattacharjee, J. Yan, B. Borhan, J. Am. Chem. Soc., 2007, 129, 1996-2003.


An intramolecular iodo-aldol cyclization of prochiral α-substituted enoate aldehydes and ketones produces hetero- and carbocycles containing quaternary centers adjacent to secondary or tertiary centers. The reactions occur in good yields and are highly trans-selective with hydroxyl and iodomethyl groups on opposite faces of the ring system.
F. Douelle, A. S. Capes, M. F. Greaney, Org. Lett., 2007, 9, 1931-1934.


A mild and convenient free-radical cyclization of organohalides in the presence of a NiCl2 • DME/Pybox complex as the catalyst and zinc powder in methanol efficiently gives carbo-, oxa-, and azacycles as products in high yields from unsaturated alkyl halides.
H. Kim, C. Lee, Org. Lett., 2011, 13, 2050-2053.


An efficient method to activate hydroxyl groups of amino alcohols has been developed, which avoids the use of toxic reagents and tolerates various functional groups. This strategy has been applied to the synthesis of functionalized p-methoxyphenyl-protected azetidines, pyrrolidines, and piperidines.
R. M. de Figueiredo, R. Fröhlich, M. Christmann, J. Org. Chem., 2006, 71, 4147-4154.


A copper(I)/ClickFerrophos complex catalyzed the asymmetric 1,3-dipolar cycloaddition of methyl N-benzylideneglycinates with electron deficient alkenes to give exo-2,4,5-trisubstituted and 2,3,4,5-substituted pyrrolidines in good yields with high diastereo- and enantioselectivities.
S.-i. Fukuzawa, H. Oki, Org. Lett., 2008, 10, 1747-1750.


An l-tert-leucine-derived AmidPhos/silver(I) catalytic system enables an asymmetric [3+2] cycloaddition of azomethine ylides with electronic-deficient alkenes. Under optimal conditions, highly functionalized endo-4-pyrrolidines were obtained in very good yields and enantioselectivities.
Z. Zhou, X. Zheng, J. Liu, J. Li, P. Wen, H. Wang, Synlett, 2017, 28, 999-1003.


Highly Endo-Selective and Enantioselective 1,3-Dipolar Cycloaddition of Azomethine Ylide with α-Enones Catalyzed by a Silver(I)/ThioClickFerrophos Complex
I. Oura, K. Shimizu, K. Ogata, S.-i. Fukuzawa, Org. Lett., 2010, 12, 1752-1755.


A successful stereochemical reversal in AgOAc catalyzed [3+2] cycloaddition is based on the formation of hydrogen bonding between ligand and reactant. Simple ligand design provides an efficient and convenient route to prepare both enantiomers of a chiral compound.
W. Zeng, G.-Y. Chen, Y.-G. Zhou, Y.-X. Li, J. Am. Chem. Soc., 2007, 129, 750-751.


Chiral complexes of calcium promote asymmetric 1,4-addition reactions and [3+2] cycloaddition reactions of α-amino acid derivatives with α,β-unsaturated carbonyl compounds. The reactions proceeded smoothly in the presence of 5-10 mol % of the chiral calcium catalyst to afford the desired adducts in high yields with high diastereo- and enantioselectivities.
S. Saito, T. Tsubogo, S. Kobayashi, J. Am. Chem. Soc., 2007, 129, 5364-5365.


Using a confined imidodiphosphate catalyst, a highly enantioselective intramolecular carbonyl-ene reaction of olefinic aldehydes delivers diverse trans-3,4-disubstituted carbo- and heterocyclic five-membered rings in high yields and with good to excellent diastereo- and enantioselectivities.
L. Liu, M. Leutzsch, Y. Zheng, M. W. Alachraf, W. Thiel, B. List, J. Am. Chem. Soc., 2015, 137, 13268-13271.


A [3 + 2]-annulation of N-Ts-α-amino aldehydes and 1,3-bis(silyl)propenes allows an efficient, stereoselective synthesis of densely functionalized pyrrolidines.
P. Restorp, A. Fischer, P. Somfai, J. Am. Chem. Soc., 2006, 128, 12646-12647.


A remarkable Pd-catalyzed diamination of unactivated alkenes using N-fluorobenzenesulfonimide (NFBS) as an aminating reagent is described. The reaction incorporates one nitrogen donor from the substrate and the other from the NFBS, thereby generating cyclic diamine derivatives in a single step. The products are differentially protected at both nitrogens, allowing for maximal synthetic flexibility.
P. A. Sibbald, F. E. Michael, Org. Lett., 2009, 11, 1147-1149.


The reaction of 1,1-cyclopropandiesters with aldimines, generated in situ by the condensation of primary amines or anilines with aldehydes, in the presence of Yb(OTf)3 as catalyst leads to pyrrolidines in good yields.
C. A. Carson, M. A. Kerr, J. Org. Chem., 2005, 70, 8242-8244.


A tandem ring-opening-cyclization reaction of cyclopropanes with imines in the presence of 5 mol% of scandium triflate was developed for the highly diastereoselective synthesis of multisubstituted pyrrolidines.
Y.-B. Kang, Y. Tang, X.-L. Sun, Org. Biomol. Chem., 2006, 4, 299-301.


An iron catalyst enables a reductive cyclization of 1,6- and 1,7-enynes. Alcohol, ketone, ester, ether, halide, amine, amide, imine, nitrile, silyl, and alkyne groups are tolerated under the mild reaction conditions. An enantioselective transformation was also conducted.
T. Xi, X. Chen, H. Zhang, Z. Lu, Synthesis, 2016, 48, 2837-2844.


Indium hydride generated from readily available Et3SiH and InCl3 offers mild conditions and low toxicity, and is therefore a promising alternative to Bu3SnH.
N. Hayashi, I. Shibata, A. Baba, Org. Lett., 2004, 6, 4981-4983.


A new methodology for the cycloisomerization of dienes using a Grubbs carbene complex and trimethylsilyl vinyl ether has been established. The utility of this reaction was demonstrated by in the synthesis of exo-methylene heterocyclic compounds, which could act as key intermediates for pharmacologically active compounds.
Y. Terada, M. Arisawa, A. Nishida, Angew. Chem. Int. Ed., 2004, 43, 4063-4067.


An enantioselective, palladium-catalyzed [3 + 2] cycloaddition of trimethylenemethane (TMM) with imines in the presence of novel phosphoramidite ligands gives the corresponding pyrrolidine cycloadducts with excellent yields and selectivities.
B. M. Trost, S. M. Silverman, J. Am. Chem. Soc., 2012, 134, 4941-4954.


FeCl2 and an iminopyridine ligand form in the presence of diethylzinc and magnesium bromide etherate an active catalyst for the reductive cyclization of 1,6-enynes to give pyrrolidine and tetrahydrofuran derivatives from N- and O-tethered 1,6-enynes.
A. Lin, Z.-W. Zhang, J. Yang, Org. Lett., 2014, 16, 386-389.


A rhodium-catalyzed asymmetric arylative cyclization of nitrogen-tethered alkyne-enoate with arylboronic acids, in which two new carbon-carbon bonds and one stereocenter are formed, provides access to pyrrolidines and piperidines with good enantioselectivities by to the use of a C1-symmetric chiral monosubstituted diene ligands.
F. Serpier, B. Flamme, J.-L. Brayer, B. Folléas, S. Darses, Org. Lett., 2015, 17, 1720-1723.


Palladium-catalyzed inter- and intramolecular enyne coupling reactions were developed. The reaction involves the acetoxypalladation of the alkyne, followed by the insertion of the alkene and the protonolysis of the carbon-palladium bond. The coupling allows the construction of synthetically important carbo- and heterocycles.
L. Zhao, X. Lu, W. Xu, J. Org. Chem., 2005, 70, 4059-4063.


A novel alkenylative cyclization of enyne was developed using Cp*RuCl(cod) under ethylene gas at room temperature.
M. Mori, N. Saito, D. Tanaka, M. Takimoto, Y. Sato, J. Am. Chem. Soc., 2003, 125, 5606-5607.


A convenient two-step preparation of alkylidenepyrrolidines is reported.
M. C. Elliot, S. V. Wordingham, Synthesis, 2006, 1162-1170.


Catalytic hydrogenation of acetylenic aldehydes using a chirally modified cationic rhodium catalysts enables highly enantioselective reductive cyclization to afford cyclic allylic alcohols. Using an achiral hydrogenation catalyst, some chiral racemic acetylenic aldehydes engage in highly syn-diastereoselective reductive cyclizations.
J. U. Rhee, M. J. Krische, J. Am. Chem. Soc., 2006, 128, 10674-10675.


Reductive radical cyclization of N-allyl-N-dimethylphosphinoyl-2-aminopropyl phenyl selenide using tris(trimethylsilyl)silane (TTMSS) / AIBN under UV irradiation gave the corresponding pyrrolidine in 74% yield and a cis/trans ratio of 10/1 which was superior to thermal cyclization
D. Shanks, S. Berlin, M. Besev, H. Ottosson, L. Engman, J. Org. Chem., 2004, 69, 1487-1491.


A chiral iridium diphosphine complex catalyzes an enantioselective intramolecular Pauson-Khand-type reaction to give various chiral bicyclic cyclopentenones. A low partial pressure of carbon monoxide is important to achieve excellent enantioselectivity.
T. Shibata, N. Toshida, M. Yamasaki, S. Maekawa, K. Takagi, Tetrahedron, 2005, 61, 9974-9979.


The reaction of various 1,6-enynes with N2CHSiMe3 in the presence of RuCl(COD)Cp* as catalyst precursor leads to the general formation of alkenylbicyclo[3.1.0]hexanes at room temperature in good yield with high stereoselectivity. The catalytic formation of alkenylbicyclo[3.1.0]hexanes also takes place in the presence of  N2CHCO2Et or N2CHPh.
F. Monnier, C. Vovard-Le Bray, D. Castillo, V. Aubert, S. Dérien, P. H. Dixneuf, L. Toupet, A. Ienco, C. Mealli, J. Am. Chem. Soc., 2007, 129, 6037-6049.


F. Monnier, C. Vovard-Le Bray, D. Castillo, V. Aubert, S. Dérien, P. H. Dixneuf, L. Toupet, A. Ienco, C. Mealli, J. Am. Chem. Soc., 2007, 129, 6037-6049.


A new Pd-catalyzed oxidation reaction for the stereospecific conversion of enynes into cyclopropyl ketones proceeds with net inversion of geometry with respect to the starting olefin. This result is consistent with a mechanism in which the key cyclopropane-forming step involves nucleophilic attack of a tethered olefin onto the PdIV-C bond.
L. L. Welbes, T. W. Lyons, K. A. Cychosz, M. S. Sanford, J. Am. Chem. Soc., 2007, 129, 5836-5837.


Enantioselective, Palladium-Catalyzed α-Arylation of N-Boc-pyrrolidine
K. R. Campos, A. Klapars, J. H. Waldman, P. G. Dormer, C.-Y. Chen, J. Am. Chem. Soc., 2006, 128, 3538-3539.