Nucleophilic 1,2‐Shifts of Carboxamide Groups in the Benzil‐Benzilic Acid Type Rearrangement of 4‐Aryl‐2,3‐dioxobutyramides and of Quinisatine

Abstract

Dedicated to Prof. Tino Giiumann on the occasion of his 6OCh birthday (25.V11.85) ~~ 4-Aryl-2,3-dioxobutyrdmide hydrates 1 undergo the benzil-benzilic acid rearrangement to form (substituted) benzyltartronate monoamides 2. For compound l a (Ar = Ph), it is demonstrated by isotopic labelling that the reaction occurs exclusively by migration of the CONH, group. Kinetic measurements with la-c and with the cyclic amide quinisatine 6 show that the rearrangement of the carboxamide group, proceeding via an alkali-catalysed step, can reach a plateau in the kOb,./[OH-] diagram (cf: the Fig.), due to complete formation of a mono-anion, and a further increase of rate attributable to the rearrangement of a bis-anion. Comparisons suggest that rearrangements involving an amide group are slower than those involving an ester group, and that, for this effect (as for others), the pre-equilibrium deprotonation of the hydrate is more important than a specific migration tendency.

Unstable 1,1,2-enetriols as (probable) intermediates in the decarboxylation of .alpha.,.beta.-diketo acids

“…(In contrast, during alkaline treatment of 2a-l-14C a benzilic acid type rearrangement with migration of the carboxamide group takes place forming Ph-CH2-C(OH)-(CONH2)COOH, which by decarboxylation yields labeled phenyllactamide and unlabeled C02). 18 The o-chloro and (14) Davis, H. W.; Grovenstein, Jr., E.; Neville, O. K. J. Am.…”