Amination of bis(trimethylsilyl)-1,2-bisketene with secondary amines: Formation of aminodihydrofuranones

The bisketene (Me3SiC=C=O)(2) (3) reacts rapidly with 1 equiv of secondary amines to form aminodihydrofuranones 11 as the only observable products. This is in contrast to previous studies (J. Org. Chem. 1999, 64, 4690) of the reactions of 3 with primary amines in which 3 with 1 equiv of amine gives ketenyl amides 4, which slowly cyclize to succinimides 7. The kinetics of the reaction of 3 with morpholine obeyed a rate law with the term [morpholine](2), consistent with rate-limiting formation of the enol amide 14 with catalysis by a second amine molecule. The subsequent formation of II is attributed to hindrance of ketonization of intermediate enol amides 14. The furanones II react with Me3SiOTf to form silyloxyfurans 16, and these react with diethyl diazodicarboxylate, forming maleamide derivatives 17.