Indene-Based Thiazolidinethione Chiral Auxiliary for Propionate and Acetate Aldol Additions

Abstract

An indene-based thiazolidinethione chiral auxiliary was prepared in two steps from trans-1-amino-2-indanol. Chlorotitanium enolates of this chiral auxiliary delivered excellent diastereoselectivities in propionate and acetate aldol additions. The chiral auxiliary was easily removed to deliver several valuable functionalities.

Synthetic Applications of Sulfur-based Chiral Auxiliaries in Asymmetric Syntheses

“…[54] This sulfur-based chiral auxiliary was prepared from commercially available trans-1-amino-2-indanol. [55] This indene-based thiazolidinethione 35 was shown to be very effective in the acetate aldol reaction with propionaldehyde to give product 36 in excellent yield and very high diastereoselectivity (Scheme 12). The N-propionyl derivative 37 was shown to work very successfully in obtaining the non-Evans aldol product 38 and also the Evans-aldol product 39.…”

Application of Oxazolidinethiones and Thiazolidinethiones in Aldol Additions

“…Thiazolidinethiones can also be prepared by exposure of the amino alcohol to sulfuric acid followed by treatment with potassium O-ethyl xanthate and aqueous base [11] or by exposure of the β-chloro amine salt to carbon disulfide and aqueous base (Scheme 7.4) [12].…”

“…The indene-derived thiazolidinethione 154 was shown to provide the anti-aldol product 155 when exposed to enolization conditions of magnesium bromide, triethylamine, and trimethylsilyl chloride as described by Evans [11]. Anti-aldol addition of N-propionylthiazolidinethione (S)-52 with cinnamaldehyde under the Evans conditions produced the TMS protected aldol adduct 156 as the only detectable isomer.…”

“…42, Scheme 7.18)[11] disclosed an indene-derived thiazolidinethione auxiliary. Each ofScheme 7.16 Tin-mediated aldol additions of acetylthiazolidinethiones and acyloxazolidinethiones.…”

Novel chiral thiazoline‐containing N―O ligands in the asymmetric addition of diethylzinc to aldehydes: substituent effect on the enantioselectivity

“…Among the large variety of Lewis basic donor functionalities, the imino moiety containing thiazoline [28][29][30][31][32] was found to an efficient surrogate to the amino unit in the chiral b-amino alcohol catalyst. However, to the best of our knowledge, there is no previous report on the development of thiazoline-containing chiral b-imino primary alcohol ligand-promoted enantioselective addition of diethylzinc to aldehydes.…”