Process for the synthesis of vinyl sulfenic acid derivatives

A process for preparing a compound of the formula ##STR22## wherein:

• R.sub.1 is hydrogen, C.sub.1 -C.sub.4 alkoxy, arylalkoxy, halo, or amino;
• R.sub.2 is hydrogen, C.sub.1 -C.sub.4 alkoxy, arylalkoxy, halo, or amino;
• R.sub.4 is OSi(R).sub.3, NR.sub.5 R.sub.6, or SR.sub.8 ;
• each R is independently C.sub.1 -C.sub.6 alkyl, aryl, or arylalkyl;
• R.sub.5 and R.sub.6 are independently hydrogen, C.sub.1 -C.sub.6 alkyl, arylalkyl, or aryl;
• or R.sub.5 and R.sub.6 together with the nitrogen atom form a ring selected from piperidine, pyrrolidine, morpholine, or hexamethylimine;
• and
• R.sub.8 is C.sub.1 -C.sub.6 alkyl, aryl, or arylalkyl;
• which comprises:
• (1) reacting a compound of the formula ##STR23## wherein:
• R.sub.1 and R.sub.2 are as defined above, and
• R.sub.3 is a thermally-labile or acid-labile C.sub.2 -C.sub.10 alkyl, C.sub.4 -C.sub.10 alkenyl, or aryl(C.sub.1 -C.sub.10 alkyl) group;
• with a silylating reagent to produce a sulfenate silyl ester of the formula ##STR24## wherein:
• R.sub.1 and R.sub.2 are as defined above;
• R.sub.7 is OSi(R).sub.3 ;
• and
• each R is independently C.sub.1 -C.sub.6 alkyl, aryl, or arylalkyl;
• (2) optionally reacting said sulfenate silyl ester with an amine of the formula HNR.sub.5 R.sub.6 wherein R.sub.5 and R.sub.6 are as defined above;
• or
• (3) optionally reacting said sulfenate silyl ester with a mercaptan of the formula HSR.sub.8, wherein R.sub.8 is as defined above, in the presence of an amine base.