Carbonylation of acyclic diaminocarbenes

点击翻译按钮获取中文摘要

The project deals with the reaction of CO with acyclic diaminocarbenes R2N-C-NR'2 (ADACs). Our results to date allow the following conclusions: It is the exception that stable or persistent ADACs are inert towards CO. Usually, they react with CO already under mild conditions, affording a highly reactive diaminoketene (R2N)(R'2N)C=C=O as the primary carbonylation product. Except in sterically highly demanding cases, subsequent nucleophilic addition of unreacted diaminocarbene to the diaminoketene takes place, affording a betainic oxyallyl system [(R2N)(R'2N)C]2CO. In sterically overcrowded cases, an intramolecular follow-up reaction takes place instead, viz. a retro-Wolff rearrangement, affording an (amino)(carboxamido)carbene R2N-C-C(O)NR'2. This undergoes an alpha-C-H insertion typical of push-pull carbenes, yielding a beta-lactam as the final product. Antibiotically active bicyclic beta-lactams, too, are accessible this way. Now our main goal is to understand the surprisingly variant reaction behaviour of ADACs which differ only marginally in their substituents. This concerns the carbonylation itself (reactive versus inert) and also the follow-up reactions of the diaminoketene, viz. betain versus beta-lactam formation. In view of the enormous relevance of bicyclic beta-lactams, a focus will be on the potential formation of such compounds in this context. An additional important goal is to identify ADACs which will give rise to stable or persistent diaminoketenes, since these compounds have great potential for Organic Synthesis.