Synthesis of substituted alkenes
The Zweifel reaction is a powerful transition-metal-free alternative to the Suzuki-Miyaura reaction for the synthesis of alkenes. This transition-metal-free coupling process enables the coupling of Grignard reagents or organolithiums for an enantiospecific synthesis of a wide variety of functionalized acyclic and cyclic olefin products.
R. J. Armstrong, W. Niwetmarin, V. K. Aggarwal, Org. Lett., 2017, 19, 2762-2765.
A selective iron-catalyzed cross-coupling of primary and secondary alkyl chlorides, bromides, and iodides with alkenylzinc reagents gives the corresponding olefins in good to excellent yields in a stereospecific manner. High functional group compatibility is also demonstrated by using combinations of substrates possessing rather reactive substituents.
T. Niu, W. Zhang, D. Huang, C. Xu, H. Wang, Y. Hu, Org. Lett., 2009, 11, 4474-4477.
N-Methyimidazole as the key additive enables high yielding stereo- and chemoselective Pd-catalyzed cross-couplings of alkenyl iodides and bromides with primary and secondary alkyl zinc iodides in THF at room temperature.
A. Krasovskiy, B. H. Lipshutz, Org. Lett., 2011, 13, 3822-3825.
A Ni-catalyzed Suzuki-Miyaura coupling of primary and secondary alkyl halides including alkyl chlorides with alkenyl-(9-BBN) reagents allows - also in combination with one pot hydroboration of terminal alkynes - the expedited synthesis of functionalized alkyl alkenes from readily available alkynes with complete (E)-selectivity.
T. Di Franco, A. Epenoy, X. Hu, Org. Lett., 2015, 17, 4910-4913.
Single-electron transmetalation via photoredox/nickel dual catalysis enables cross-coupling of primary and secondary (bis-catecholato)alkylsilicates with alkenyl halides via transfer of alkyl radicals under very mild reaction conditions. The method works with not only alkenyl bromides and iodides but also previously underexplored alkenyl chlorides.
N. R. Patel, C. B. Kelly, M. Jouffroy, G. A. Molander, Org. Lett., 2016, 18, 764-767.
A method to produce 1,2-disubstituted olefins in high Z selectivity via reductive cross-coupling of alkyl halides with terminal arylalkynes employs inexpensive and nontoxic catalyst (iron(II) bromide) and reductant (zinc). The substrate scope encompasses primary, secondary, and tertiary alkyl halides, and the reaction tolerates a large number of functional groups.
C. W. Cheung, F. E. Zhurkin, X. Hu, J. Am. Chem. Soc., 2015, 137, 4932-4935.
The stereochemical outcome of Negishi coulings of Z-alkenyl halides is highly ligand dependent. A modified method solves the stereochemical issue and significantly improves yields of Negishi couplings in general even at ambient temperature.
A. Krasovskiy, B. H. Lipshutz, Org. Lett., 2011, 13, 3818-3821.
Sarcosine is an excellent ligand for cobalt-catalyzed carbon-carbon cross-coupling of Grignard reagents with allylic and vinylic bromides. The system performs efficiently when phenyl and benzyl Grignards are coupled with alkenyl bromides. Notably, previously unachievable Co-catalyzed coupling of allylic bromides with Grignards to linearly coupled α-products was also realized.
R. Frlan, M. Sova, S. Gobec, G. Stavber, Z. Časar, J. Org. Chem., 2015, 80, 7803-7809.
A nonionic amphiphile (PTS) enables a simple approach to Pd-catalyzed stereoselective sp3-sp2 cross-couplings between alkyl and alkenyl bromides in the presence of zinc powder in water to give coupled products in good yields without prior formation of the organozinc reagents. The reaction is conducted at room temperature and tolerates various functional groups.
A. Krasovskiy, C. Duplais, B. H. Lipshutz, Org. Lett., 2010, 12, 4742-4744.
An alkenylation of alkyl electrophiles using nearly stoichiometric amounts of air- and moisture-stable potassium organotrifluoroborates tolerates various functional groups on both the nucleophilic and electrophilic partner. Reactions of highly substituted E- and Z-alkenyltrifluoroborates, as well as vinyl- and propenyltrifluoroborates, were successful with retention of stereochemistry and regiochemistry.
G. A. Molander, O. A. Argintaru, Org. Lett., 2014, 16, 1904-1907.
The presence of FeCl3/CuTC enables an efficient coupling of functionalized aryl Grignard reagents and 1-arylvinyl halides to access 1,1-diarylethylenes of biological interest. This bimetallic system proved to be superior to the use of Fe or Cu catalyst alone. The synthetic utility of this protocol is illustrated in the field of steroid chemistry.
A. Hamze, J.-D. Brion, M. Alami, Org. Lett., 2012, 14, 2782-2785.
The use of 2% Pd2(dba)3/8% PCyp3/NMI in THF/NMP at 80°C achieves the cross-coupling of a range of β-hydrogen-containing primary alkyl iodides, bromides, chlorides, and tosylates with an array of alkyl-, alkenyl-, and arylzinc halides. This method tolerates various functional groups.
J. Zhou, G. C. Fu, J. Am. Chem. Soc., 2003, 125, 12527-12530.
An insoluble, amphiphilic and polymeric palladium catalyst (PdAS) is an excellent catalyst for the Suzuki-Miyaura reaction. The catalyst is reusable after easy work up and showed good stability in any reaction medium.
Y. M. A. Yamada, K. Takeda, H. Takashashi, S. Ikegami, J. Org. Chem., 2003, 68, 7733-7741.
"Ligandless" palladium complexes can catalyze the zirconium-Negishi reactions of alkyl electrophiles. Ligandless processes offer low cost, simplicity, and ease of purification.
S. L. Wiskur, A. Korte, G. C. Fu, J. Am. Chem. Soc., 2004, 126, 82-83.
A combination of nickel(II) acetylacetonate and (Z)-3,3-dimethyl-1,2-bis(diphenylphosphino)but-1-ene catalyzes cross-coupling reactions of alkyl aryl sulfides and alkenyl alkyl sulfides with primary and secondary alkyl Grignard reagents.
S. Kanemura, A. Kondoh, H. Yorimitsu, K. Oshima, Synthesis, 2008, 2659-2660.
A copper-catalyzed hydroalkylation of terminal alkynes using alkyl triflates as coupling partners and (Me2HSi)2O as a hydride donor proceeds with excellent anti-Markovnikov regioselectivity and provides exclusively (E)-alkenes. Both alkyl- and aryl-substituted alkynes can be used as substrates, together with 1° alkyl and benzylic triflates. Finally, the transformation can be accomplished in the presence of a wide range of functional groups.
M. R. Uehling, A. M. Suess, G. Lalic, J. Am. Chem. Soc., 2015, 137, 1424-1427.
In the presence of Co(PPh3)2I2, PPh3, water, and zinc powder, the reductive coupling of alkynes with alkenes having an electron-withdrawing substituent proceeded smoothly in acetonitrile to give the corresponding reductive coupling products in fair to excellent yields. Possible mechanisms for this highly regio- and stereoselective ene-yne reaction are proposed.
C.-C. Wang, P.-S. Lin, C.-H. Cheng, J. Am. Chem. Soc., 2002, 124, 9696-9697.
Use of a zirconocene catalyst based on the Brintzinger ligand and catalytic amounts of methyl aluminoxanes (MAO) effect a >99% regiocontrol of Negishi carboaluminations of 1-alkynes in toluene.
B. H. Lipshutz, T. Butler, A. Lower, J. Am. Chem. Soc., 2006, 128, 15396-15398.
In a copper-catalyzed formal carboboration of alkynes, a C-B bond and a C-C bond are created in a single catalytic cycle. The reaction proceeds with high regioselectivity and syn-stereoselectivity to form tri- and tetrasubstituted vinylboronic esters from commercially available bis(pinacolato)diboron. A subsequent cross-coupling reaction gives access to highly substituted alkenes.
R. Alfaro, A. Parra, J. Alemán, J. L. G. Ruano, M. Tortosa, J. Am. Chem. Soc., 2012, 134, 15165-15168.
In a copper-catalyzed regio- and stereoselective borylalkylation of dialkylsubstituted internal alkynes with bis(pinacolato)diboron and alkyl halides, a borylcopper species containing a novel π-accepting N-heterocyclic carbene ligand chemoselectively reacted with unactivated internal alkynes over alkyl halides. The intermediate alkenylcopper species subsequently reacted with alkyl halides, affording the desired products.
T. Itoh, Y. Shimizu, M. Kanai, J. Am. Chem. Soc., 2016, 138, 7528-7531.
The use of the Xantphos ligand in a mild palladium-catalyzed Kumada-Corriu reaction of secondary benzylic bromides with aryl and alkenyl Grignard reagents minimizes the undesired β-elimination pathway. The corresponding cross-coupling products can be isolated in good yields with inversion of the configuration.
A. López-Pérez, J. Adrio, J. C. Carretero, Org. Lett., 2009, 11, 5514-5517.
A Ni-catalyzed asymmetric reductive cross-coupling between vinyl bromides and benzyl chlorides provides direct access to enantioenriched products bearing aryl-substituted tertiary allylic stereogenic centers from simple, stable starting materials. A broad substrate scope can be converted under mild reaction conditions without pregeneration of organometallic reagents and the regioselectivity issues commonly associated with allylic arylation.
A. H. Cherney, S. E. Reisman, J. Am. Chem. Soc., 2014, 136, 14365-14366.
An enantioselective Ni-catalyzed cross-coupling of N-hydroxyphthalimide esters with vinyl bromides proceeds under mild conditions and uses tetrakis(N,N-dimethylamino)ethylene as a terminal organic reductant. Good functional group tolerance is demonstrated, with over 20 examples of reactions that proceed with excellent enantioselectivity.
N. Suzuki, J. L. Hofstra, K. E. Poremba, S. E. Reisman, Org. Lett., 2017, 19, 2150-2153.
The air-stable nickel(II) complex trans-(PCy2Ph)2Ni(o-tolyl)Cl enables an internally selective Mizoroki-Heck-type coupling of substituted benzyl chlorides with terminal alkenes at room temperature. This operationally simple and highly regioselective reaction provides rapid, convergent access to substituted allylbenzene derivatives in high yield and can be carried out on the benchtop with no purification or degassing of solvents or reagents.
E. A. Standley, T. F. Jamison, J. Am. Chem. Soc., 2013, 135, 1585-1592.
Nickel-catalyzed intermolecular benzylation and heterobenzylation of unactivated alkenes with benzyl chlorides provides functionalized allylbenzene derivatives. In contrast to analogous palladium-catalyzed processes, all reactions described herein employ electronically unbiased aliphatic olefins (including ethylene), proceed at room temperature, and provide 1,1-disubstituted olefins with very high selectivity.
R. Matsubara, A. C. Gutierrez, T. F. Jamison, J. Am. Chem. Soc., 2011, 133, 19020-19023.
The palladium-catalyzed reaction of allyl acetates with aryl- and vinyltin reagents gave good yields of cross-coupled products. The reaction was mild and tolerant of functionality (-CO2R, -OH, -OSiR3, -OMe) in the tin reagent. Inversion of stereochemistry at the acetate center was observed, with retention of the geometry of the olefin of the allyl group and with exclusive coupling at the primary position. Retention of geometry of the olefin in the vinyltin reagents was also observed.
L. Del Valle, J. K. Stille, L. S. Hegedus, J. Org. Chem, 1990, 55, 3019-3023.
Bromoboration of propyne with BBr3 proceeds in syn-selectivity to produce (Z)-2-bromo-1-propenyldibromoborane, which is prone to stereoisomerization. Treatment with pinacol yields the stable and storable pinacolboronate. Negishi coupling gives trisubstituted (Z)-alkenylpinacolboronates in good yields. Iodinolysis of the boronates affords alkenyl iodides in good yields.
C. Wang, T. Tobrman, Z. Xu, E.-i. Negishi, Org. Lett., 2009, 11, 4092-4095.
C-O bond cleavage of lithium alkoxides occurs readily at room temperature in the presence of titanium(IV) halides. Capture of the resultant carbocation by alkynes provides an efficient route to trisubstituted (E)-alkenyl halides with high stereoselectivity.
M.-L. Yao, T. R. Quick, Z. Wu, M. P. Quinn, G. W. Kabalka, Org. Lett., 2009, 11, 2647-2649.
A robust copper-catalyzed or transition-metal-free alkylation of gem-difluoroalkenes with alkyl Grignard reagents proceeded very smoothly in the presence of 25 mol % of CuCN or under transition-metal-free conditions. Especially tertiary and secondary alkyl-substituted fluoroalkenes can be isolated in good to excellent yields with excellent Z stereoselectivity.
W. Dai, H. Shi, X. Zhao, S. Cao, Org. Lett., 2016, 18, 4284-4287.
An easy access to (Z)-trisubstituted allylic alcohols is based on E to Z isomerization of 1-bromo-1-dialkylvinylboranes upon reaction with dialkylzinc reagents. Subsequent transmetalation to give (Z)-trisubstituted vinylzinc species is followed by trapping with aldehydes to furnish a series of (Z)-trisubstituted allylic alcohols.
Y. K. Chen, P. J. Walsh, J. Am. Chem. Soc., 2004, 126, 3702-3703.
An efficient Fe(III)-catalyzed direct coupling of alkenes with alcohols and cross-coupling of alcohols with alcohols gives the corresponding substituted (E)-alkenes stereospecifically. Mild conditions, atom efficiency, environmental soundness, and stereospecificity are features that make this procedure very attractive. Additionally, this reaction could be scaled up.
Z.-Q. Liu, Y. Zhang, L. Zhao, Z. Li, J. Wang, H. Li, L.-M. Wu, Org. Lett., 2011, 13, 2208-2211.
An efficient Cu(OTf)2-catalyzed sp3-sp2 coupling of propargylic alcohols with terminal alkenes gives a diverse range of 1,4-enynes in very good yields. The reaction is tolerant to air and atom-economical.
G.-B. Huang, X. Wang, Y.-M. Pan, H.-S. Wang, G.-Y. Yao, Y. Zhang, J. Org. Chem., 2013, 78, 2742-2745.
The use of bisphosphine ligands with a large P-Pd-P bite angle allowed to synthesize Z-chlorinated internal alkenes in good yields by a selective Suzuki-Miyaura monocoupling process of 9-alkyl-9-BBN with 1,1-dichloro-1-alkenes. These monochlorinated olefins could be further transformed providing stereospecifically trisubstituted olefins.
F. Liron, C. Fosse, A. Pernolet, E. Roulland, J. Org. Chem., 2007, 72, 2220-2223.
An additive-free, clean conjugate addition reaction of organosiloxanes to α,β-unsaturated compounds is catalyzed by a cationic rhodium complex in dioxane/water. The mechanism involves a transmetalation step between the rhodium complex and the silicon reagent.
S. Oi, Y. Honma, Y. Inoue, Org. Lett., 2002, 4, 667-669.
C2-symmetric chiral diene ligands based on a 3,7-disubstituted bicyclo[3.3.1]nona-2,6-diene readily bind to rhodium(I). These rhodium complexes act as effective catalysts for 1,4-addition of alkenyl- and arylboronic acids to various α,β-unsaturated ketones, including several combinations that were previously difficult to provide high enantioselectivity.
R. Shintani, Y. Ichikawa, K. Takatsu, F.-X. Chen, T. Hayashi, J. Org. Chem., 2009, 74, 869-873.
A Pd-catalyzed three-component reaction of 3-(pinacolatoboryl)allyl acetates, aldehydes, and organoboranes provides (Z)-anti-homoallylic alcohols with high levels of diastereoselectivity and alkene stereocontrol.
Y. Horino, A. Aimono, H. Abe, Org. Lett., 2015, 17, 2824-2827.
Conjugate addition of dimethyl alkenylboronates to α,β-unsaturated ketones in the presence of catalytic amounts of 3,3'-disubstituted binaphthols provides alkenylation products in good yields and high enantioselectivities.
T. R. Wu, J. M. Chong, J. Am. Chem. Soc., 2007, 129, 4908-4909.
A direct conjugate addition of simple alkenes to enones has been achieved in the presence of a Ni(0)/PCy3 catalyst. This reaction is a straightforward method for the introduction of an alkenyl group at the β-position of enones.
S. Ogoshi, T. Haba, M. Ohashi, J. Am. Chem. Soc., 2009, 131, 10350-10351.
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.
An efficient highly regio- and stereoselective iron-catalyzed conjugate addition of 2,3-allenoates with primary or secondary alkyl, phenyl, or vinyl Grignard reagents gives multi-substituted β,γ-unsaturated enoates in good yields. The in situ formed magnesium dienolate may readily react with different electrophilic reagents to construct an allylic quaternary carbon at the α-position of the ester group.
Z. Lu, G. Chai, S. Ma, J. Am. Chem. Soc., 2007, 129, 14546-14547.
Reductive coupling of enones or enals with alkynes using reducing agents such as organozincs, organoboranes, organosilanes, and methanol is cost-effective, and tolerant of many functional groups. Isotopic labeling strategies have provided supporting evidence for the mechanistic proposals.
W. Li, A. Herath, J. Montgomery, J. Am. Chem. Soc., 2009, 131, 17024-17029.
A nickel-catalyzed intermolecular reductive coupling of enones and alkynes gives γ,δ-unsaturated ketones. The process does not require formation of a vinyl organometallic, and a variety of functional groups including free hydroxyls and esters are tolerated.
A. Herath, B. B. Thompson, J. Montgomery, J. Am. Chem. Soc., 2007, 129, 8712-8713.
A three-component nickel-catalyzed coupling of enals, alkynes, and silanes forms an enol silane and a trisubstituted alkene with >98:2 stereoselectivity. The reaction tolerates a broad range of functionality including aldehydes, ketones, esters, free hydroxyls, and basic secondary amines.
A. Herath, J. Montgomery, J. Am. Chem. Soc., 2008, 130, 8132-8133.
A conjugate addition of organosiloxanes to α,β-unsaturated carbonyl compounds catalyzed by a cationic rhodium complex generated from [Rh(cod)(MeCN)2]BF4 and (S)-BINAP in dioxane/water gave products in good yields and excellent enantioselectivities.
S. Oi, A. Taira, Y. Honma, Y. Inoue, Org. Lett., 2003, 5, 97-99.
Treatment of 2,2-dimethylpropan-1,3-diol esters of aryl- and alkenylboronic acids with a catalytic amount of [Rh(OH)(cod)]2 in the presence of 1,3-bis(diphenylphosphino)propane and CsF in dioxane at 60°C under carbon dioxide atmosphere gave carboxylic acids in good yields.
K. Ukai, M. Aoki, J. Takaya, N. Iwasawa, J. Am. Chem. Soc., 2006, 128, 8706-8707.
Catalyzed by a chiral palladium complex, 1,1-bis(pinacolboronate) esters undergo asymmetric cross-coupling with bromoalkenes to generate allyl boronates with high levels of enantioselectivity. Oxidation of these allyl boronates with hydrogen peroxide provides secondary allylic alcohols, whereas nitrosobenzene as oxidant furnishes nonracemic tertiary allylic alcohols.
B. Potter, A. A. Szymaniak, E. K. Edelstein, J. P. Morken, J. Am. Chem. Soc., 2014, 136, 17918-17921.
A palladium-catalyzed double coupling of nitromethane with vinyl triflates and bromide generates homo allyl nitro products via a tandem cross-coupling/π-allylation sequence. The resultant process exploits the anion stabilizing and leaving group properties of nitromethane and provides a mild and convenient entry to nitroethylated products, which are versatile precursors to β,γ-unsaturated carbonyls, homoallylic amines, and nitrile oxides.
R. Padilla-Salinas. R. R. Walvoord, S. Tcyrulnikov, M. C. Kozlowski, Org. Lett., 2013, 15, 3966-3969.
A highly regio- and stereoselective coupling of (Z)-1,2-bis(aryl(alkyl)thio)alkenes and Grignard reagents in the presence of a Ni catalyst under mild conditions enables an efficient route for the synthesis of (Z)-vinylic sulfides. (Z)-vinylic sulfides are important intermediates in the synthesis of tri- and tetrasubstituted alkenes.
J. Chen, S. Chen, X. Xu, Z. Tang, C.-T. Au, R. Qiu, J. Org. Chem., 2016, 81, 3246-3255.
An efficient iron-catalyzed cross-coupling of primary alkyl Grignard reagents allows the use of alkenyl and aryl pivalates as electrophiles under mild conditions. The combination of an inexpensive and stable carboxylate electrophile and an iron catalyst would generate ample advantages.
B.-J. Li, L. Xu, Z.-H. Wu, B.-T. Guan, C.-L. Sun, B.-Q. Wang, Z.-J. Shi, J. Am. Chem. Soc., 2009, 131, 14656-14657.
On exposure to BuLi, 3-bromo-2-iodocyclopent-2-enol O-TBS ether undergoes iodine-lithium permutation with complete regioselectivity. Reaction with different electrophiles affords the corresponding 2-substituted-3-bromocyclopentenol derivatives. Subsequent bromo-lithium exchange with t-BuLi, followed by reaction with an equal or different electrophile, affords 2,3-disubstituted cyclopentenols.
M. Luparia, A. Vadalà, G. Zanoni, G. Vidari, Org. Lett., 2006, 8, 2147-2150.
Opening of the epoxide ring of enantiopure (2R,1'S)-2-(1-aminoalkyl)epoxides with different organolithium compounds gave allylamines with total selectivity and in high yields.
J. M. Concellon, J. R. Suarez, V. del Solar, Org. Lett., 2006, 8, 349-351.
A cobalt-catalyzed photochemical synthesis of allylic trifluoromethanes from styrene derivatives using 2,2,2-trifluoroethyl iodide complements existing approaches, providing an alternative bond construction strategy to access these compounds. The process may be conducted in continuous mode in a photochemical flow reactor.
L. M. Kreis, S. Krautwald, N. Pfeiffer, R. E. Martin, E. M. Carreira, Org. Lett., 2013, 15, 1634-1637.
An operationally simple Pd-catalyzed three component reaction involving terminal alkynes, boronic acids, and perfluoroalkyl iodides gives trisubstituted perfluoroalkenes in a highly regio- and stereocontrolled manner by simultaneous additions across the triple bond in a radical-mediated process. The reaction is broad in scope and tolerates many functional groups.
Z. Li, A. García-Domínguez, C. Nevado, J. Am. Chem. Soc., 2015, 137, 11610-11613.