Highly Stereoselective Intermolecular Oxy‐Michael Addition Reaction to α,β‐Unsaturated Malonate Esters.

Abstract

Hydroxycarboxylic acids (ether carboxylic acids) and estersHydroxycarboxylic acids (ether carboxylic acids) and esters P 0280Highly Stereoselective Intermolecular Oxy-Michael Addition Reaction to α,β-Unsaturated Malonate Esters. -The naked anion of enantiopure lactol (I) undergoes highly diastereoselective oxy-Michael additions to a range of alkylidiene-, arylidene-, and heteroarylidenemalonate esters. The reactions occur under kinetic control in THF at -78 °C and provide a complementary but direct asymmetric route to protected β-hydroxy ester products. Subsequent acid-mediated deprotection affords the enantioenriched aldol products in quantitative yields. -

Nanoporous Aluminosilicate-Catalyzed Telescoped Acetalization-Direct Aldol Reactions of Acetals with 1,3-Dicarbonyl Compounds

“…18,19 The lack of suitable aldol protocols has led to the development of alternative synthetic strategies to access β-hydroxycarbonyl products, such as the oxy-Michael addition reaction of alkoxide nucleophiles under strongly basic conditions. 20 Our interest in this area was prompted by the observation that acyclic acetals undergo direct aldol reactions with activated methylene compounds in the presence of strong Lewis acids at very low reaction temperatures to give the corresponding addition products (Scheme 1). 21 The reaction of carbonyl derivatives, such as acetals and acylals, as surrogates for carbonyl compounds is a surprisingly mature area 22,23 and is a useful strategy for carbon−carbon bond formation albeit one that has been comparatively under exploited.…”