Synthesis of Five-Membered Cyclic Phosphinic Acids via the [4C+1P] Cyclization of 1,3-Dienes with a Combination of PBr3 and P(OMe)3 as the P(III) Source

Anefficient method for the synthesis of 1-hydroxy-2,5-dihydrophosphole1-oxides, a type of five-membered P-containing heterocycliccompound, is presented. The reaction was carried out through a [4C+1P]cyclization of 1,3-dienes with a combination of PBr3 andP(OMe)(3) as the P-(III) source. To compare withthe reported methods, the protocol reported herein not only is muchmilder and more rapid but also displays a broad substrate scope andaffords the products in high yields (50-94%). In addition,the reaction could be reliably scaled up at the gram-scale level andwas demonstrated to be a versatile platform for flexible derivatization.Consequently, this method provides a general and reliable way forthe synthesis of five-membered phosphole derivatives.