Synthesis and Oxidation Reactions of Thiazol‐2‐thione‐fused 1,4‐Dihydro‐1,4‐diphosphinines

Backbone (Et 2 N) 2 P‐substituted thiazol‐2‐thione 2 [(Et 2 N) 2 P‐THS Me ; THS Me =3‐methylthiazol‐2‐thione‐5‐yl] was employed in a stepwise reaction to access thiazol‐2‐thione‐fused tricyclic 1,4‐dihydro‐1,4‐diphosphinines 5   a,a’ {–[P(Et 2 N)THS Me ] 2 ; optimization efforts led to excellent yields of 5   a,a’ if LDA was used as the base. The same protocol could be exploited to access P ‐Ph derivatives 5   c,c’‐d,d’ {–[P(Ph)THS R ] 2 . Oxidation reactions of 5   a,a’ using H 2 O 2 ‐urea, sulfur and grey selenium furnished the bis( P ‐oxides) 6,6’ , bis( P ‐sulfides) 7,7’ , and bis( P ‐selenides) 8,8’ , respectively. Reaction of 5   a,a’ with o ‐chloranil led stereoselectively to bis(spirophosphorane) derivatives 9,9’ .