Nucleophilic Napththalene Dearomatization of N-Alkyl-N-benzyl(dinaphthyl)phosphinamides. Application to the Synthesis of γ-(N-Alkylamino) (dihydronaphthalenyl)phosphinic Acids

Abstract

Lithiation of N-alkyl-N-benzyl(dinaphthyl)phosphinamides with s-BuLi at -90 ºC in THF promoted the dearomatization of one naphthalene ring through anionic cyclization. The intermediate lithium compounds were trapped with MeOH, MeI and allyl bromide affording benzo[e]-1-phosphaisoindoles with excellent stereoselectivities. Acid hydrolysis of the P-N linkage allowed to obtain γ-(N-alkylamino)phosphinic acids containing a dihydronaphthalene system. This structural fragment proved to be an element of conformational restriction.