Interaction of 1,3,2,4‐Benzodithiadiazines with Aromatic Phosphines and Phosphites

Abstract

ABSTRACT Although an interaction between hydrocarbon and fluorocarbon 1,3,2,4‐benzodithiadiazines ( 1 ) and P(C 6 H 5 ) 3 continuously produces chiral 1,2,3‐benzodithiadiazol‐2‐yl iminophosporanes ( 2 ; in this work, 5,7‐difluoro derivative 2a ) via 1:1 condensation, an interaction between 1 and other PR 3 reagents gives different products. With R  OC 6 H 5 and both hydrocarbon and fluorocarbon 1 , only X=P(OC 6 H 5 ) 3 (X = S, O) were identified in the complex reaction mixtures by 13 С and 31 Р NMR and GC‐MS. With R = C 6 F 5 , no interaction with the archetypal 1 was observed but catalytic addition of atmospheric water to the heterocycle afforded 2‐amino‐ N ‐sulfinylbenzenesulfenamide ( 4 ). With electrophilic B(C 6 F 5 ) 3 instead of nucleophilic P(C 6 F 5 ) 3 , only adduct H 3 N→B(C 6 F 5 ) 3 and a new polymorph of C 6 F 5 B(OH) 2 were isolated and identified by X‐ray diffraction (XRD). A molecular structure of 2a was confirmed by XRD, and the π‐stacked orientation of one of phenyl groups and heterocyclic moiety was observed. This structure is in general agreement with that calculated at the RI‐MP2 level of theory, as well as at three different levels of DFT theory with the PBE and B3LYP functionals. Mild thermolysis of 2a in a dilute decane solution gave persistent 5,7‐difluoro‐1,2,3‐benzodithiazolyl ( 3a ) identified by EPR in combination with DFT calculations.