Reactions of the activated, rigid, α‐diazomethine group of 1,2,5‐thiadiazole 1,1‐dioxides with nitrogenated nucleophiles. Part III: aliphatic monoamines and phenylhydrazine

The reactions of n ‐butylamine (BuNH 2 ), 2‐aminoethanol (H 2 N(CH 2 ) 2 OH), diethylamine (Et 2 NH), and phenylhydrazine (PhN 2 H 3 ) with 3,4‐diphenyl‐( 1a ) and phenanthro[9,10‐c]‐1,2,5‐thiadiazole 1,1‐dioxide ( 1b ) were studied by cyclic voltammetry (CV) and 1 H‐ and 13 C‐NMR in aprotic solvent solution. The course of the reactions depended on the substrate‐nucleophile combination: Et 2 NH added to 1a or 1b , forming the corresponding thiadiazolines in an equilibrium monoaddition reaction. The equilibrium constants were evaluated and compared. With primary amines and PhN 2 H 3 , the nucleophile added to both CN double bonds of 1a and displaced the sulfamide moiety. In the case of the reaction of 1a with PhN 2 H 3 , the intermediate monoaddition thiadiazoline, 3‐(2‐phenylhydrazino)‐3,4‐diphenyl‐1,2,5‐thiadiazoline 1,1‐dioxide, was also isolated. BuNH 2 and H 2 N(CH 2 ) 2 OH reacted with 1a to give α‐bis‐imines, while 1a with PhN 2 H 3 gave the α‐bis‐hydrazone. The configurations of benzil bis(ethanolimine) and benzilosazone were determined by single crystal x‐ray diffraction analysis as Z,Z. BuNH 2 and PhN 2 H 3 reduced 1b to the corresponding thiadiazoline compound 1b H 2 . Copyright © 2006 John Wiley & Sons, Ltd.