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Synthesis of substituted allenes

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1,3-Substitution with carbon nucleophiles

Recent Literature

Sulfonate-bearing chiral bidentate N-heterocyclic carbene (NHC) complexes of copper enable catalytic enantioselective allylic substitutions of allylic phosphonates with commercially available allenylboronic acid that result in addition of an allenyl group and formation of tertiary or quaternary C-C bonds in up to 95% yield, >98% S_N2′ selectivity, and 98% ee.
B. Jung, A. H. Hoveyda, J. Am. Chem. Soc., 2012, 134, 1490-1493.

Lithiation of 1-aryl-3-alkylpropadienes and subsequent transmetalation with zinc bromide followed by Pd-catalyzed Negishi coupling reactions with halides afforded the corresponding trisubstituted allenes in a highly regioselective fashion with good yields. A plausible regioselective lithiation mechanism was proposed on the basis of deuterium labeling experiments.
J. Zhao, Y. Liu, S. Ma, Org. Lett., 2008, 10, 1521-1523.

1,1-diarylpropadienes and 1,3-diarylpropynes can be prepared by the sequential lithiation of 1-aryl-1-propynes, transmetalation, and the corresponding Pd(0)-catalyzed cross-coupling with aryl halides.
S. Ma, Q. He, X. Zhang, J. Org. Chem., 2005, 70, 3336-3338.

Tertiary homopropargyl alcohols can be used as allenylmetal equivalents in a palladium-catalyzed reaction with aryl halides to provide arylallenes regioselectively. The reaction includes retro-propargylation, which proceeds in a concerted fashion via a cyclic transition state and transfers the stereochemistry of homopropargyl alcohols through C-C bond cleavage.
S. Hayashi, K. Hirano, H. Yorimitsu, K. Oshima, J. Am. Chem. Soc., 2008, 130, 5048-5049.

Arynes, generated in situ from ortho-silylaryl triflates, undergo ene reaction with alkynes possessing propargylic hydrogen in the presence of KF/18-crown-6 in THF at room temperature to give substituted phenylallenes in good to moderate yields.
T. T. Jayanth, M. Jeganmohan, M.-J. Cheng, S.-Y. Chu, C.-H. Cheng, J. Am. Chem. Soc., 2006, 128, 2232-2233.

Various arylallenes and alkenylallenes were prepared via coupling of allenylstannanes with aryl iodides or alkenyl iodides in the presence of Pd(PPh₃)₄ as catalyst, LiCl, and DMF as solvent.
C.-W. Huang, M. Shanmugasundaram, H.-M. Chang, C.-H. Cheng, Tetrahedron, 2003, 59, 3635-3641.

A cyclopentadienyliron dicarbonyl complex catalyzes a functionalization of the C(sp²)-H bonds of monosubstituted alkylallenes with aldehydes in the presence of triisopropylsilyl triflate to provide 1,1-disubstituted allenylic triisopropylsilyl ethers in good yields. Lithium bistriflimide was identified as a critical additive in this transformation.
R. Ding, Y. Wang, Y.-M. Wang, Synthesis, 2023, 55, 733-743.

A site-selective cyanation of the sp² C-H bond of allenes using a copper-catalyzed radical relay affords various allenyl nitriles directly from simple allenes with a broad substrate scope and a remarkable functional group compatibility under mild conditions. The excellent site-selectivity toward can be attributed to the unique pocket created by the Cu-bound nitrogen-centered radical.
Z. Cheng, T. Yang, C. Li, Y. Deng, F. Zhang, P. Chen, Z. Lin, S. Ma, G. Liu, J. Am. Chem. Soc., 2023, 145, 25995-26002.

Pd-catalyzed cross-coupling reactions of electron-rich and electron-poor aryl iodides with organoindium reagents generated in situ from indium and ethyl 4-bromo-2-alkynoates produced selectively ethyl 2-aryl-2,3-alkadienoates in good yield.
P. H. Lee, J. Mo, D. Kang, D. Eom, C. Park, C.-H. Lee, Y M. Jung, H. Hwang, J. Org. Chem., 2011, 76, 312-315.

Using a Pd-catalyzed divergent cyclization, including cycloisomerization and aerobic oxidative cycloisomerization of homoallenyl amides, varieties of functionalized 2-amino-5-alkylfurans and 2-amino-5-formylfurans can be selectively synthesized in very good yields. The mild reaction conditions, high atom economy, and utilization of air as the oxygen source make this protocol very environmentally benign and practical.
C. Cheng, S. Liu, G. Zhu, Org. Lett., 2015, 17, 1581-1584.

Low loadings of an in situ generated B-based catalyst, that is derived from a simple, robust, and readily accessible chiral aminoalcohol, promote an enantioselective addition of an allene unit to aldimines. Various aryl-, heteroaryl-, and alkyl-substituted homoallenylamides can be obtained in very good yield and high enantiomeric excess at ambient temperature using a commercially available allenylboron reagent.
H. Wu, F. Haeffner, A. H. Hoveyda, J. Am. Chem. Soc., 2014, 136, 3780-3781.

A one-step, three-component condensation of allenyl boronic acids or allenyl pinacolboronates with amines and aldehydes affords α-allenyl or α-propargyl α-amino acids and anti-β-amino alcohols. Secondary amines generate exclusively α-allenyl α-amino acids, while primary aliphatic amines lead to α-propargyl α-amino acids.
F. Liepouri, G. Bernasconi, N. A. Petasis, Org. Lett., 2015, 17, 1628-1631.

Borono-Mannich reactions of pinacol allenylboronate with salicylaldehyde and amines are highly regioselective and give homopropargylamine for secondary amines and α-allenylamine products for primary amines, respectively. In contrast, glycoaldehyde and chiral α-hydroxyaldehydes give exclusively anti-β-amino-β-allenyl alcohol products, irrespective of the nature of the amine component.
T. Thaima, S. G. Pyne, Org. Lett., 2015, 17, 778-781.

Addition of α-alkenylzirconacyclopentenes to aldehyde enables a highly stereoselective synthesis of β-hydroxyallenes with multiple stereogenic centers including allenic axial chirality, as well as center chirality. Remarkably, the reaction occurs with completely different chemoselectivity in comparison with the usual alkyl- or aryl-substituted zirconacyclopentenes.
Y. Zhou, J. Chen, C. Zhao, E. Wang, Y. Liu, Y. Li, J. Org. Chem., 2009, 74, 5326-5330.

Reactions of various carbonyl compounds with organoindium reagent in situ generated from indium and 1-bromopent-4-en-2-yne derivatives gives functionalized vinyl allenols in good yields. Treatment of vinyl allenols with gold catalyst, dienophile, or indium trihalide produced functionalized dihydrofuran, cyclohexene, or 2-halo-1,3-diene derivatives in very good yields.
J. Park, S. Hong, P. H. Lee, Org. Lett., 2008, 10, 5067-5070.

A catalytic enantioselective conjugate addition of commercially available allenylboronic acid pinacol ester as nucleophile to α,β-unsaturated carbonyl compounds is promoted by a chiral copper NHC complex.
Q. Chong, S. Zhang, F. Cheng, J. Wang, X. Hong, F. Meng, Org. Lett., 2018, 20, 6896-6900.

N-Methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene (MTBD) catalyzes a Morita-Baylis-Hillman reaction of previously hard-to-activate α,γ-dialkyl allenoate substrates. The obtained densely substituted allenic alcohols could be further converted into 2,5-dihydrofuran and 2H-pyran-2-one heterocyclic structures with challenging substitution patterns.
P. Selig, A. Turočkin, W. Raven, Synlett, 2013, 24, 2535-2539.

A AuCl-catalyzed, flexible synthesis of highly substituted, benzyl-protected phenols unites enal/enones and benzyl allenyl ethers in a [3+3] fashion in two steps, allowing excellent control of substitution at the benzene ring.
X. Huang, L. Zhang, Org. Lett., 2007, 9, 4627-4630.

Homoallenic alcohols are prepared from various propargyl vinyl ethers using a trinuclear gold(I)-oxo complex, [(Ph₃PAu)₃O]BF₄, as a catalyst for propargyl Claisen rearrangement at room temperature.
B. D. Sherry, F. D. Toste, J. Am. Chem. Soc., 2004, 126, 15978-15979.

Interruption of Formal Schmidt Rearrangement/Hosomi-Sakurai Reaction of Vinyl Azides with Allyl/Propargylsilanes
G. Fang, Z. Liu, S. Cao, H. Yuan, J. Zhang, L. Pan, Org. Lett., 2018, 20, 7113-7116.

Copper catalyzes a regioselective synthesis of allenyl monofluorides with inexpensive and accessible aryl boronic esters under mild conditions. Arylated allenyl monofluorides were stable enough to be isolated and easily converted to various other fluorine-containing compounds.
Y. You, J. Hu, T. Wu, Org. Lett., 2023, 25, 4546-4550.