Synthesis of cyclopentanes
Reduction of stilbenes with Na metal in dry THF allowed easy access to various 1,2-diaryl-1,2-disodiumethanes. These diorganometallic intermediates gave 1,2-diarylethanes upon aqueous work up, or trans-1,2-diaryl-substituted cyclopentanes by cycloalkylation with 1,3-dichloropropanes.
U. Azzena, G. Dettori, C. Lubinu, A. Mannu, L. Pisano, Tetrahedron, 2005, 61, 8663-8668.
Microscale parallel experimentation was used to discover catalyst systems capable of coupling secondary organotrifluoroborates with aryl chlorides and bromides. A ligand-dependent β-hydride elimination/reinsertion mechanism was implicated in the cross-coupling of more hindered substrates, leading to isomeric mixtures of coupled products in some cases.
S. D. Dreher, P. G. Dormer, D. L. Sandrock, G. A. Molander, J. Am. Chem. Soc., 2008, 130, 9257-9259.
A stannane, which is simple to prepare, was successfully used in standard radical reactions as replacement of Bu3SnH and Ph3SnH. The tin-containing byproducts are removed by mild hydrolysis and extraction with aqueous NaHCO3. The performance of this new reagent was tested for reactions involving halides, selenides, Barton-McCombie deoxygenation and enyne cyclization.
D. L. J. Clive, J. Wang, J. Org. Chem., 2002, 67, 1192-1198.
A copper hydride-catalyzed, enantioselective, intramolecular hydroalkylation of halide-tethered styrenes enables the synthesis of enantioenriched cyclobutanes, cyclopentanes, indanes, and six-membered N- and O-heterocycles.
Y.-M. Wang, N. C. Bruno, A. L. Placeres, S. Zhu, S. L. Buchwald, J. Am. Chem. Soc., 2015, 137, 10524-10527.
A route to trisubstituted olefins through a palladium-catalyzed alkyne insertion with unactivated alkyl iodides followed by a reduction proceeds under mild conditions and tolerates a range of functional groups and substitution patterns. Mechanistic inquiry suggests that the transformation proceeds through a hybrid radical/organometallic pathway.
E. R. Fruchey, B. M. Monks, A. M. Patterson, S. P. Cook, Org. Lett., 2013, 15, 4362-4365.
N-heterocyclic carbenes catalyze intramolecular β-alkylations of α,β-unsaturated esters, amides, and nitriles that bear pendant leaving groups to form a variety of ring sizes. The mechanism is discussed.
C. Fischer, S. W. Smith, D. A. Powell, G. C. Fu, J. Am. Chem. Soc., 2006, 128, 1472-1473.
A simple, chemoselective Ni-catalyzed reductive cyclization/carboxylation of unactivated alkyl halides with CO2 operates under mild conditions.
X. Wang, Y. Liu, R. Martin, J. Am. Chem. Soc., 2015, 137, 6476-6479.
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.
Stereospecific, nickel-catalyzed Heck cyclizations of secondary benzylic ethers proceeds in high yield and enantiospecificity to yield enantioenriched methylenecyclopentanes for benzylic ethers of both π-extended and simple arenes.
M. R. Harris, M. O. Konev, E. R. Jarvo, J. Am. Chem. Soc., 2014, 136, 7825-7828.
Cobalt complex/Zn systems effectively catalyze the reductive coupling of activated alkenes with alkynes in the presence of water to give substituted alkenes with very high regio- and stereoselectivity in excellent yields.
H.-T. Chang, T. T. Jayanth, C.-C. Wang, C.-H. Cheng, J. Am. Chem. Soc., 2007, 129, 12032-12041.
InCl3 and (Cy)(i-Pr)NH efficiently promote the carbocyclization reaction of α-disubstituted aldehydes to give functionalized cyclopentanes in very good yields through a combination of enamine-type catalysis with an indium-catalyzed activation of alkynes.
B. Montaignac, M. R. Vitale, V. Michelet, V. Ratovelomanana-Vidal, Org. Lett., 2010, 12, 2582-2585.
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 chiral iron(III)-salen complex catalyzes an asymmetric Conia-ene-type cyclization of α-functionalized ketones containing an unactivated terminal alkyne and produces an exo-methylenecyclopentane scaffold possessing a stereodefined quaternary center.
S. Shaw, J. D. White, J. Am. Chem. Soc., 2014, 136, 13174-13177.
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 Ni(II)-catalyzed Conia-ene reaction of various acetylenic 1,3-dicarbonyl compounds has been discovered. The reaction gave mono- and bicyclic olefinic cyclopentantes in good yields in the presence of Ni(acac)2 and Yb(OTf)3.
Q. Gao, B.-F. Zheng, J.-H. Li, D. Yang, Org. Lett., 2005, 7, 2185-2188.
[ReBr(CO)3(thf)]2 catalyzed the reactions of 1,3-dicarbonyl compounds with terminal acetylenes, which gave the corresponding alkenyl derivatives in excellent yields.
Y. Kuninobu, A. Kawata, K. Takai, Org. Lett., 2005, 7, 4823-4825.
A relay strategy, in which ring-closing metathesis and bifunctional chiral amine (thio)urea-catalyzed Michael addition reactions proceed in a one-pot fashion, offers an alternative approach to the synthesis substituted cyclopentanes in good yields and good enantioselectivities.
Y. Zhang, X. Song, X. Chen, A. Song, S. Zhang, W. Wang, Synthesis, 2014, 46, 2601-2607.
An enantioselective Conia-ene reaction of acetylenic β-dicarbonyl compounds employs a DTBMSegphos-Pd(II)/Yb(III) dual catalyst system that allows for the asymmetric synthesis of all-carbon quaternary centers and generates a methylene cyclopentane containing an alkene that can be further manipulated.
B. K. Corkey, F. D. Toste, J. Am. Chem. Soc., 2005, 127, 17168-17169.
Nitroalkenes readily undergo palladium-catalyzed [3 + 2] cycloaddition with trimethylenemethane to generate nitrocyclopentanes in excellent yield and enantioselectivity. Nitrocyclopentanes are highly versatile synthetic intermediates and provide convenient access to both cyclopentylamines and cyclopentenones.
B. M. Trost, D. A. Bringley, P. S. Seng, Org. Lett., 2012, 14, 234-237.
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 novel approach to 3(2H)-furanones combines a transition-metal-catalyzed activation of alkynes with a heterocyclization and subsequent 1,2-alkyl shift. Starting 2-hydroxy-2-alkynylcarbonyl compounds can be prepared by simple oxygenation of alkynyl carbonyl compounds using 2-iodoxybenzoic acid (IBX).
S. F. Kirsch, J. T. Binder, C. Liébert, H. Menz, Angew. Chem. Int. Ed., 2006, 45, 5878-5880.
Cobalt-catalyzed transformations of cyclic alkenes such as cyclopentene and cycloheptene with internal alkynes led to a chemoselective Alder-ene or a [2 + 2] cycloaddition reaction depending on the electronic nature of the alkyne and the bite angle of a bidentate phosphine ligand used.
G. Hilt, A. Paul, J. Treutwein, Org. Lett., 2010, 12, 1536-1539.
Ru(bipy)3Cl2 is a visible light photocatalyst for [2+2] enone cycloadditions. Various aryl enones participate readily in the formation of the cyclobutane products, and the diastereoselectivity is excellent. A mechanism is proposed in which a photogenerated Ru(bipy)3+ complex promotes one-electron reduction of the enone substrate, which undergoes subsequent radical anion cycloaddition.
M. A. Ischay, M. E. Anzovino, J. Du, T. P. Yoon, J. Am. Chem. Soc., 2008, 130, 12886-12887.
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.