Selective Alkynylallylation of the C-C sigma Bond of Cyclopropenes

摘要

A Pd-catalyzed regio- and stereoselective alkynylallylation of a specific C-C sigma bond in cyclopropenes, using allyl propiolates as both allylation and alkynylation reagents, has been achieved for the first time. By merging selective C(sp(2))-C(sp(3)) bond scission with conjunctive cross-couplings, this decarboxylative reorganization reaction features fascinating atom and step economy and provides an efficient approach to highly functionalized dienynes from readily available substrates. Without further optimization, gram-scale products can be easily obtained by such a simple, neutral, and low-cost catalytic system with high TONs. DFT calculations afford a rationale toward the formation of the products and indicate that the selective insertion of the double bond of cyclopropenes into the C-Pd bond of ambidentate Pd complex and the subsequent nonclassical beta-C elimination promoted by 1,4-palladium migration are critical for the success of the reaction.