81286-89-7Relevant academic research and scientific papers
α-ALKYLATION OF α-HETEROSUBSTITUTED CARBOXYLIC ACIDS WITHOUT RACEMIZATION; EPC-SYNTHESES OF TERTIARY ALCOHOLS AND THIOLS
Seebach, Dieter,Naef, Reto,Calderari, Giorgio
, p. 1313 - 1324 (2007/10/02)
α-Hydroxy- and α-mercapto-carboxylic acids are condensed with pivalaldehyde to give 2-t-butyl-5-substituted-1,3-dioxolanones or 1,3-oxathiolanones (2); the predominate cis-isomers are separeted by crystallization.The cis-disubstituted heterocycles 2 derived from lactic, mandelic and malic acid funish, after deprotonation with LDA, reaction with electrophiles such as alkyl halides, aldehydes and ketones, and hydrolysis α-branched α-hydroxy-carboxylic acids (3, 6, 8, 9, 10).These result from an overall substitution of the proton in the α-CO position with retention of configuration.The optically active carboxylic acids are α-alkylated without racemization and without employment of a chiral auxiliary ("self-reproduction of chirality", Scheme 1).The diastereoselectivities (ds) are generally >95percent (Table 1, 2, and 20-25).
Enantioselective Generation and Diastereoselective Reactions of Chiral Enolates Derived from α-Heterosubstituted Carboxylic Acids
Seebach, Dieter,Naef, Reto
, p. 2704 - 2708 (2007/10/02)
Dioxolanones 7 and 8a and oxazolinones 9a derived from pivalaldehyde and lactic acid, mandelic acid, and proline, respectively, furnish chiral enolates of type 3 by deprotonation with LDA.Reactions of these enolates with alkyl halides, aldehydes, and keto
