Structure–property-reactivity studies on dithiaphospholes

The reaction of either toluene-3,4-dithiol or benzene dithiol with phosphorus( iii ) trihalides generates the corresponding benzo-fused 1,3,2-dithiaphospholes, RC 6 H 3 S 2 PX (R = Me ( 1 ), R = H ( 2 ); X = Cl, Br, I). The P -chloro-dithiaphospholes undergo: (a) halogen abstraction reactions with Lewis acids forming phosphenium cations; (b) substitution with LiHMDS base and; (c) reduction chemistry with sodium metal to generate the P–P σ-bonded dimer, (RC 6 H 3 S 2 P) 2 . Reduction catalysis of aldehydes with pinacolborane using dithiaphospholes is compared with their dioxaphosphole and diazaphosphole counterparts as pre-catalysts, revealing interesting differences in the reactivity of this series of compounds.