Stereoselective reduction of the ketone group in α-allyl β-keto esters
摘要:
Stereoselective reduction of the ketone carbonyl group in alpha-allyl-substituted beta-keto esters with sodium tetrahydridoborate in the presence of 2 equiv of MnCl2 quantitatively afforded the corresponding syn-isomeric alcohols. The reduction of the same substrates with L-selectride [LiBH(s-Bu)(3)] in anhydrous THF was characterized by low chemoselectivity, and anti-isomeric alcohols were formed in about 50% yield. Under analogous conditions, alpha-allyl ketones smoothly reacted with L-selectride to give syn-isomeric alcohols in quantitative yield. The corresponding anti isomers were synthesized by the Mitsunobu reaction of the syn isomers with formic acid, followed by alkaline hydrolysis.
Stereoselective reduction of the ketone group in α-allyl β-keto esters
作者:V. I. Boev、A. I. Moskalenko、S. L. Belopukhov、N. M. Przheval’skii
DOI:10.1134/s1070428015090067
日期:2015.9
Stereoselective reduction of the ketone carbonyl group in alpha-allyl-substituted beta-keto esters with sodium tetrahydridoborate in the presence of 2 equiv of MnCl2 quantitatively afforded the corresponding syn-isomeric alcohols. The reduction of the same substrates with L-selectride [LiBH(s-Bu)(3)] in anhydrous THF was characterized by low chemoselectivity, and anti-isomeric alcohols were formed in about 50% yield. Under analogous conditions, alpha-allyl ketones smoothly reacted with L-selectride to give syn-isomeric alcohols in quantitative yield. The corresponding anti isomers were synthesized by the Mitsunobu reaction of the syn isomers with formic acid, followed by alkaline hydrolysis.
On the Scope of a<i>Prins</i>-Type Cyclization of Oxonium Ions
作者:Georg Fráter、Urs Müller、Philip Kraft
DOI:10.1002/hlca.200490248
日期:2004.11
The Prins cyclization of an aldehyde 1 with a homoallylic alcohol 2, affording tetrahydro-2H-pyrans 4via the oxoniumion 3 as central intermediate, was conceptually transferred to (alk-3-enyloxy)acrylates 6, which form a related oxoniumion 7 upon treatment with acids (Scheme 1). The scope and utility of this modification of the Prins-type cyclization of oxoniumions is discussed exemplarily by means