Untersuchungen zur stereoselektiven elektrophilen Cyanierung

Abstract

Studies on Stereoselective Electrophiic Cyanation The enantioselective, electrophilic cyanation of the enolates of 2‐substituted 1‐tetralones 3 is described. Enantiomerically pure 2‐cyanato‐1,1′‐binaphthyl derivatives 2, 6a and b are used as cyanating agents. The influence of solvent, temperature, additives and the method of enolate formation are investigated. Best results are obtained with 48% ee in the case of compound 2 and 60% ee in the case of compound 6b if the enolate is prepared from the corresponding silyl enol ether 7 and Toluene is used as solvent.

Electrophilic Cyanation of Boron Enolates: Efficient Access to Various β‐Ketonitrile Derivatives

“…Apractical method for the electrophilic cyanation of ketones often employs enolates or enolate equivalents as the nucleophile. [10,11] Lithium enolates can react with ptoluenesulfonyl cyanide (TsCN) and phenyl cyanate, [12] but these methods were also limited to the use of cyclic ketone derivatives.A lthough the reaction of silyl enolates with ah ypervalent-iodine-based cyanating reagent has recently been reported, [13] the method still remains limited to anarrow substrate scope and low efficiency. [10,11] Lithium enolates can react with ptoluenesulfonyl cyanide (TsCN) and phenyl cyanate, [12] but these methods were also limited to the use of cyclic ketone derivatives.A lthough the reaction of silyl enolates with ah ypervalent-iodine-based cyanating reagent has recently been reported, [13] the method still remains limited to anarrow substrate scope and low efficiency.…”

Enantioselective Electrophilic Cyanation of Boron Enolates: Scope and Mechanistic Studies

“…To achieve such reactions, the enantioselective electrophilic cyanation of ketone enolate equivalents has been developed in recent years. However, the methods reported to date are limited to the cyanation of cyclic 1,3‐dicarbonyl compounds (Scheme c) with the only one exception, in which the reaction of tetralone‐derived lithium enolates proceeded with moderate enantioselectivity …”

“…However, the methods reported to date are limited to the cyanation of cyclic 1,3-dicarbonyl compounds( Scheme1c) [7] with the only one exception, in which the reactiono ft etralone-derived lithium enolates proceeded with moderate enantioselectivity. [8] This limitation is due to the difficulties of both the stereoselective preparation of the essential a,a-disubstituted enolates neededf or the reaction as well as the subsequent enantioselective cyanation. Therefore, the enantioselective electrophilic cyanation of ketone-derived enolatesr emains largely undeveloped and continues to be ac hallenging task (Scheme 1d).…”

Highly Enantioselective α‐Cyanation with 4‐Acetylphenyl Cyanate

“…Herein, we reporto ur methodologyf or the enantioselective acyanation for b-keto esters and amidesb earing five-or sixmembered rings (Scheme1b).We knew that the racemic reaction could be catalyzed by Lewis acids. [5a] To gether with the knowledge of the good solubility and mild reactivity of cyanate, [8,9] we chose phenylcyanate as the cyano source to developt he asymmetric version with at ransition-metal complex as the catalyst. Initially, am odel reaction of b-keto ester 1d [10] and 4-acetyl phenylcyanate (C2)w as performed in the presence of ab isoxazolinebased zinc complex.…”