Synthesis of β-hydroxy ketones and aldehydes
Rhodium-catalyzed catalytic hydrogenation of methyl vinyl ketone (MVK) and ethyl vinyl ketone (EVK) in the presence of various aldehydes at ambient temperature and pressure using tri-2-furylphosphine as ligand enables formation of aldol products with high levels of syn-diastereoselectivity. Hydrogen-labile functional groups, including alkynes, alkenes, benzylic ethers, and nitroarenes, remain intact under the coupling conditions.
C.-K. Jung, S. A. Garner, M. J. Krische, Org. Lett., 2006, 8, 519-522.
A tandem 1,4-reduction-aldol cyclization is induced by exposure of monoenone monoketones to catecholborane in THF at ambient temperature. Six-membered cyclic aldol products are formed in excellent yield with high levels of syn diastereoselectivity for aromatic and heteroaromatic enones. Five-membered ring formation proceeds less readily, but the yield is improved through addition of Rh(I) salts.
R. R. Huddleston, D. F. Cauble, M. J. Krische, J. Org. Chem., 2003, 68, 11-14.
The reaction of α-bromoaldehydes with aldehydes in the presence of GeCl2-dioxane gave cross-aldol equivalents with syn-selectivity. The initially formed β-germoxyaldehydes did not lead to side products. Addition of a catalytic amount of Bu4NBr improved the yield and selectivity.
M. Yusada, S.-Y. Tanaka, A. Baba, Org. Lett., 2005, 7, 1845-1848.
The addition of bromomagnesium 2-vinyloxy ethoxide to various aldehydes in the presence of 10 mol% Sc(OTf)3 provides a broad range of functionalized protected aldol compounds. A Swern oxidation-CBS reduction sequence enables the preparation of chiral protected aldol products.
P. Quinio, L. Kohout, D. S. Roman, J. Gaar, K. Karahiosoff, P. Knochel, Synlett, 2016, 27, 1715-1719.
Mild and selective heterobimetallic-catalyzed decarboxylative aldol reactions of allyl β-keto esters with aldehydes are promoted by Pd(0)- and Yb(III)-DIOP complexes at room temperature. The optimized reaction conditions require the addition of both metals.
S. Lou, J. A. Westbrook, S. E. Schaus, J. Am. Chem. Soc., 2004, 126, 11440-11441.
An Et3SiH-promoted diastereoselective reductive aldol reaction has been developed using InBr3 as a catalyst. This three-component reaction afforded only silyl aldolates as products without any side reactions.
I. Shibata, H. Kato, T. Ishida, M. Yasuda, A. Baba, Angew. Chem. Int. Ed., 2004, 43, 711-714.
The Rh-catalyzed reaction of 9-aryl-9-borabicyclo[3.3.1]nonanes with α,β-unsaturated ketones and aldehydes gave high yields of tandem 1,4-addition-aldol reaction products with high syn selectivity. The mechanism is discussed.
K. Yoshida, M. Ogasawara, T. Hayashi, J. Am. Chem. Soc., 2002, 124, 10984-10985.
A proazaphosphatrane is a very efficient catalyst for Mukaiyama aldol reactions of aldehydes with trimethylsilyl enolates in THF solvent. The reaction conditions are mild and operationally simple, and a variety of aryl functional groups, such as nitro, amino, ester, chloro, trifluorometh yl, bromo, iodo, cyano, and fluoro groups, are tolerated.
V. R. Chintareddy, K. Wadhwa, J. G. Verkade, J. Org. Chem., 2009, 74, 8118-8132.
An indium triiodide catalyst promoted the Mukaiyama Aldol Reaction of silyl enolates with esters to form β-hydroxycarbonyl compounds in the presence of hydrosilanes. Various esters were applicable, and the high chemoselectivity of this system brings compatibility to many functional groups, such as alkenyl, alkynyl, chloro, and hydroxy.
Y. Inamoto, Y. Nishimoto, M. Yasuda, A. Baba, Org. Lett., 2012, 14, 1168-1171.
Hydroxymethylation of dimethylsilyl (DMS) enolates using aqueous formaldehyde solution is catalyzed by scandium(III) fluoride in aqueous media to give the corresponding β-hydroxy ketones in good to excellent yields, but TMS enolates react sluggishly under the same conditions. ScF3 has been shown to be a unique catalyst for this reaction.
M. Kokubo, S. Kobayashi, Synlett, 2008, 1562-1564.
The synthesis of new C1-symmetric benzene-bridged aminosulfoximines is described. These aminosulfoximines are capable of serving as efficient ligands in copper-catalyzed enantioselective Mukaiyama-type aldol reactions.
M. Langner, C. Bolm, Angew. Chem. Int. Ed., 2004, 43, 5984-5987.
A new, diastereoselective three-component halo aldol reaction has been discovered for the tandem formations of I-C/C-C bonds, which gives aldol adducts in good yields. The key intermediates (allenolates and 1-iodo-3-siloxy-1,3-butadienes), were directly monitored by 1H NMR.
H.-X. Wei, S. H. Kim, G. Li, Org. Lett., 2002, 4, 3691-3693.