Enantioselective cyanoformylation of aldehydes catalyzed with solid base mediated chiral V(V) salen complexes

Abstract

Polymeric and monomeric V(V) chiral salen complexes-catalyzed enantioselective ethyl cyanoformylation of aldehydes using ethyl cyanoformate as a source of cyanide was accomplished in the presence of several basic cocatalysts viz., NaOH, KOH, basic Al2O3 and hydrotalcite. Excellent yield (>95%) of chiral ethyl cyanohydrincarbonate with high enantioselectivity up to 94% was achieved in 24-36 h when hydrotalcite was used as an additive. The polymeric catalyst 1 is more reactive than the monomeric catalyst 2 to produce chiral ethyl cyanohydrincarbonate in high optical purity. The chiral polymeric catalyst 1 and cocatalysts hydrotalcite and basic alumina used in this study were recoverable and recyclable several times with retention of its performance.

Asymmetric Catalysis Using Chiral Salen–Metal Complexes: Recent Advances

“…Polymeric catalyst 44 was also employed in asymmetric cyanoformylation of aldehydes using ethyl cyanoformate as the source of cyanide (Scheme 11). 25 The basic additive hydrotalcite enhances the yield of (S)-ethyl cyanohydrin carbonate products (>95%), and enantiomeric excess up to 94% is achieved. In a comparison of polymeric catalyst 44 with its monomeric counterpart 42, the former is more reactive, producing cyanohydrin carbonates in higher optical purity.…”

Dimeric & Polymeric Chiral Schiff Base Complexes and Supported BINOL Complexes as Potential Recyclable Catalysts in Asymmetric Kinetic Resolution and C–C Bond Formation Reactions

“…The polymeric catalyst 39 was found to be more reactive than the monomeric catalyst 41 to produce chiral ethyl cyanohydrincarbonate in high optical purity ( Complex 37 Fig. 15 Cyanide addition to carbonyl compound using dimeric salen complexes [137] HT/basic alumina used in this study were recoverable and recyclable several times with the retention of its performance [142].…”

Making Chiral Salen Complexes Work with Organocatalysts

“…The group of Khan 43 tackled the challenge of working out a procedure leading to the efficient and easy recovery of the bicatalytic system for its reuse. They thus prepared a polymeric vanadium salen catalyst 7 from an enantiopure salen polymeric ligand possessing methylene spacers that was already shown to be easily recoverable by simple precipitation in hexane (Scheme 10).…”