Unprecedented Tandem Conjugate Addition/C‐O Ester Migration of α‐Cyano Arylacetates with a Quinone Monoimine

Abstract

An unprecedented conjugate addition/CÀ O ester migration of α-cyano arylacetates with a quinone monoamine was presented, which allowed for the synthesis of various 2,2-diarylacetonitriles in moderate to quantitative yields. This method is applicable to a series of α-cyano arylacetates with different aryl groups. Moreover, in order to demonstrate the synthetic utility of this transformation, 2-(cyano(phenyl))-4-(4-methylphenylsulfonamido)ethyl carbonate was subjected in hydrogenation to generate a 2,2-diarylethylcarbamate.Quinone derivatives are highly electrophilic and can react with many nucleophilic reagents. In the past few years, the research of reactions of quinone derivatives have attracted more and more interest and impressive progress has been made. [1,2] Our group has also been working on developing of new transformations of quinone derivatives. [2p-r] α-Substituted α-cyano acetates are good nucleophiles and have been widely used in the construction of densely functionalized compounds. [3.4] However, up to now, there is only one report about reaction of α-cyano acetates with quinone derivatives. Chandra and co-workers recently reported an organocatalytic asymmetric conjugate addition/cyclization of p-quinone diimides with α-cyano acetates, which afforded various cyclic imidines in good yields with moderate to good enantioselectivities (Scheme 1, a). [2c] As a part of our ongoing exploration of new transformations involving quinone derivatives, we also studied the reaction of α-cyano arylacetates with a quinone monoimine. To our surprise, an unprecedented tandem conjugate addition/CÀ O ester migration occurred and a kind of novel 2,2-diarylacetonitriles were obtained in moderate to quantitative yields (Scheme 1, b). CÀ O ester migration of α-nitro acetates has been reported previously. [5] However, to the best of our knowledge, up to now, there is no report about CÀ O ester migration of α-cyano acetates. Therefore, this is the first time that CÀ O ester migration of α-cyano acetates was presented.First, we initiated the reaction of ethyl á-cyano phenylacetate 1 a with quinone monoimine 2 a in acetonitrile at room temperature. The reaction provided the product 3 a with moderate yield in 18 hours (Table 1, entry 1). The structure of [a] Dr.

Tandem Reaction of Phenyl α‐Cyano‐α‐arylacetates with Quinone Monoimines

“…The reactions generated various cyclic imidines in good yield with moderate to good ee values (Scheme 1, a) [6a] . Next we demonstrated an unprecedented tandem conjugate addition/C−O ester migration of ethyl α ‐cyano arylacetates with a quinone monoimine and a kind of novel 2,2‐diarylacetonitriles were obtained in moderate to quantitative yields (Scheme 1, b) [6b] …”

“…As an on‐going research on transformations of quinone derivatives and α ‐cyano acetates, herein we used phenyl α ‐cyano‐ α ‐arylacetates in reaction with quinone monoimines. Interestingly, unlike the previous work, [6b] in the presence of catalytic amount of DABCO, the substrates underwent a tandem reaction to generate various 2‐aminobenzofuran derivatives in low to moderate yields (Scheme 1, c).…”

Recent Advances in the Domino Annulation Reaction of Quinone Imines

“…Zhang et al also developed a divergent reaction between para -quinone monoimines 3 and α-cyano-α-arylacetates 112 . In 2019, they found that tandem conjugate addition and C–O ester migration occurred in refluxing acetonitrile to give various 2,2-diarylacetonitriles in generally good yields (not shown) [ 76 ]. In 2021, they found that an organic base could also promote the [3 + 2] cycloaddition reaction of para -quinone monoimines 3 with α-cyano-α-arylacetates 112 but resulted in the formation of 2-aminobenzofuran 113 , which was protected with di- tert -butyl dicarbonate to give 114 in moderate to good yields ( Scheme 25 ) [ 77 ].…”