Rhodium(I)‐Catalyzed Azide‐Alkyne Cycloaddition (RhAAC) of Internal Alkynylphosphonates with High Regioselectivities under Mild Conditions

A regioselective method to access fully substituted 1,2,3‐triazolyl‐4‐phosphonates from the internal alkynylphosphonates by rhodium(I)‐catalyzed azide‐alkyne cycloaddition (RhAAC) under mild conditions is reported. This approach is water and air compatible and has a broad substrate scope, good functional group tolerance, high yields and excellent regioselectivities. Fully substituted 1,2,3‐triazolyl‐4‐phosphonates are directly prepared from the internal alkynylphosphonates by RhAAC with high 1,4‐regioselectivities. The gram‐scale preparation, application to carbohydrate synthesis and the solid‐phase synthesis of triazolyl‐4‐phosphonates are highlights of this method.