Studies on the reactive organotitanium intermediates and chiral 1,1′-Binaphthyl-2,2′-diamine derivatives

Abstract

This thesis entitled ?Studies on the Reactive Organotitanium Intermediates and Chiral 1,1and#8242;-Binaphthyl-2,2and#8242;-Diamine Derivatives? comprises of two parts. Each part is subdivided into two chapters under four sections namely Introduction, Results and Discussion, Conclusions and Experimental Section along with References. The work described in this thesis is exploratory in nature and the chapters are arranged in the order the investigations were executed. In Part I, investigations on the titanium reagents are described. Results of studies on the use of the TiCl4/Et3N reagent system for the preparation of chiral enolates for use in Mannich-type reaction are described in Chapter 1. The reaction of L-(-)-menthyl butyrate 1 and imines 2a-g with the TiCl4/Et3N reagent system gave the corresponding syn-and#946;-amino esters 3-9 in moderate to good yields with good selectivity (Scheme 1). The major amino ester products 3a and 9a were characterized by the single crystal X-ray analysis of the corresponding mandelic acid salt. The compound 3a has been found to be useful for the resolution of the racemic mandelic acid to gt99% ee in a single step. The syn-and#946;-amino ester 3a was debenzylated using Pd/C in formic acid/methanol mixture under ambient condition (Scheme 2). The corresponding and#946;-amino acid 11 was obtained in 44% yield by acid hydrolysis of the syn-and#946;-amino ester 3a (Scheme 3). The and#946; lactam 12 was prepared by the reaction of syn-and#946;-amino ester 3a with ethylmagnesium bromide. Partial racemization of the and#946;-lactam product 12 was observed (Scheme 4). Studies on the titanium complex promoted reactions of donor-acceptor cyclopropanes 13 and 15 are described in Chapter 2. The cycloaddition reaction of cyclopropyl ketone 13 and imine 2a in the presence of TiCl4 gave the corresponding pyrrolidine ketone 14 in 54% yield (Scheme 5). The intermediate prepared using cyclopropyl diester 15 and TiCl2(OiPr)2 on reaction with imines 2a-e gave the corresponding pyrrolidines 16 - 20 (Scheme 6).