Enantioselective Assembly of Fully Substituted α-Amino Allenoates Through a Mannich Addition and Stepwise [3,3]-σ...

Chiral fully-substituted allenes are synthetically significant and pivotal building blocks that can engage in diverse transformations toward a variety of bioactive molecules. The enantioselective assembly of these skeletons using readily available reactants offers significant advantages but remains challenging. Herein, an asymmetric formal Michael-type addition of alkynyl imines with the key alkylgold intermediates derived in situ from N-propargylamides is accomplished under gold-complex and chiral quinine-derived squaramide (QN-SQA) synergetic catalysis. Control experiments and the density functional theory (DFT) calculations indicated that this cascade reaction involves a Mannich-type addition and stepwise [3,3]-σ rearrangement sequence, leading to the fully substituted α-amino allenoates, which are elusive and take multi-step to prepare with other methods, in high yields and excellent enantioselectivity.