Base-Controlled Cu-Catalyzed Tandem Cyclization/Alkynylation for the Synthesis of Indolizines

A base-controlled Cu-catalyzed tandem cyclization/alkynylation of propargylic amines provides rapid access to functionalized indolizine derivatives under mild reaction conditions. The reaction first proceeded via a 5-endo-dig aminocupration, followed by a coupling between the copper bound intermediate and alkynyl bromide, to afford the products in good to excellent yields. The successful tandem reaction is attributed to the unique property of the bases, DBU (1,8-diazabicyclo[5.4.0]undec-7-ene) and MTBD (7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene used).