Synthesis of allyl ketones and aldehydes
A selective coupling of alkynylsilanes and allyltrimethylsilane is catalyzed by 5 mol% of indium tribromide under mild conditions to afford the corresponding α,β-acetylenic ketones and β,γ-unsaturated ketones in excellent yields.
J. S. Yadav, B. V. S. Reddy, M. Sridhar Reddy, G. Parimala, Synthesis, 2003, 2390-2394.
A highly regio- and enantioselective copper-catalyzed three-component coupling of isocyanides, hydrosilanes, and γ,γ-disubstituted allylic phosphates/chlorides provides chiral α-quaternary formimides in the presence of a chiral naphthol-carbene ligand and LiOtBu as base. The formimides can readily be converted to α-quaternary aldehydes.
K. Hojoh, H. Ohmiya, M. Sawamura, J. Am. Chem. Soc., 2017, 139, 2184-2187.
A Cu-catalyzed hydroalumination of readily accessible allenes with diisobutylaluminum hydride provides allylaluminum reagents under mild reaction conditions. A subsequent tandem nucleophilic addition to aldehydes/Oppenauer oxidation enables a one-pot synthesis of allylic ketones with α-tertiary and α-quaternary centers.
S. Lee, S. Lee, Y. Lee, Org. Lett., 2020, 22, 5806-5810.
Substituted allylic zinc reagents, prepared via direct metal insertion in substituted allylic halides, react readily with a broad range of acid chlorides and chloroformates to yield the corresponding α-substituted β,γ-unsaturated ketones and esters in high yield and perfect regioselectivity.
C. Sämann, P. Knochel, Synthesis, 2013, 45, 1870-1876.
Tandem Ru-catalysis enables the coupling of internal alkynes with aldehydes for the synthesis of β,γ-unsaturated ketones with high regioselectivity. The catalyst for example differentiates between methyl and ethyl substituent on the alkyne.
Q.-A. Chen, F. A. Cruz, V. M. Dong, J. Am. Chem. Soc., 2015, 137, 3157-3160.
A cobalt-catalyzed hydroacylation of 1,3-dienes with non-chelating aromatic aldehydes provides 1,4-addition products as the major isomer, while aliphatic aldehydes favor 1,2-hydroacylation products. The kinetic profile supports an oxidative cyclization mechanism involving a cobaltacycle intermediate that undergoes transformation with high regio- and stereoselectivity.
Q.-A. Chen, D. K. Kim, V. M. Dong, J. Am. Chem. Soc., 2014, 136, 3772-3775.
Under the conditions of ruthenium-catalyzed transfer hydrogenation, 1,3-dienes couple to benzylic and aliphatic alcohols and aldehydes to deliver β,γ-unsaturated ketones in very good yields. In all cases, complete branch regioselectivity is observed.
F. Shibahara, J. F. Bower, M. J. Krische, J. Am. Chem. Soc., 2008, 130, 14120-14122.
An efficient cross-addition reaction of dienes with aldehydes in the presence of RuHCl(CO)(PPh3)3 as catalyst gives various β,γ-unsaturated ketones. A π-allylruthenium species, derived from hydroruthenation of the diene, may be involved as a key intermediate.
S. Omura, T. Fukuyama, J. Horiguchi, Y. Murakami, I. Ryu, J. Am. Chem. Soc., 2008, 130, 14094-14095.
Commercially available chiral ligands enable a widely applicable, practical, and scalable strategy for efficient and enantioselective synthesis of β,γ-unsaturated ketones that contain an α-stereogenic center.
J. del Pozo, S. Zhang, F. Romiti, S. Xu, R. P. Conger, A. H. Hoveyda, J. Am. Chem. Soc., 2020, 142, 18200-18212.
An efficient, practical photocatalytic deoxygenation/defluorination protocol provides γ,γ-difluoroallylic ketones from commercially available aromatic carboxylic acids and α-trifluoromethyl alkenes in the presence of triphenylphosphine. The protocol offers good functional group tolerance and a broad substrate scope.
Y.-Q. Guo, R. Wang, H. Song, Y. Liu, Q. Wang, Org. Lett., 2020, 22, 709-713.