New anellated 4H-1,4,2-diazaphospholes

Abstract

Five new anellated 4H-1,4,2-diazaphospholes including the first examples of chiral 4H-1,4,2-diazaphospholes with the (−)-menthyl substituent have been prepared by two main routes: Hantzsch type cyclocondensation of 4-phenyl-2-amino-1,3-thiazole with chloromethyl dichlorophosphine and 4+1 cyclocondensation of cycloimmonium salts derived from 4-phenyl-2-amino-1,3-thiazole and 2-aminopyridine with PCl₃ and NEt₃. The new compounds have been characterized by multinuclear (¹H, ¹³C, ³¹P) NMR spectroscopy. Controlled hydrolysis of 5-phenylthiazolo[3,2-d][1,4,2]diazaphosphole 2a with two equivalents of water yields the corresponding zwitterionic phosphinate 9, the structure of which was elucidated by single crystal X-ray diffraction. The structure in the solid state is governed by strong N–H⋯O hydrogen bonding resulting in chains along the crystallographic a-axis. The chloroform molecules are integrated in the chains by weaker C–H⋯O bonds and C–Cl⋯C halogen bonds.