Synthesis of sulfonamide intermediates

A process for making a compound of formula:

• ##STR4## wherein:
• R is H or Cl;
• and
• R' is C.sub.1-6 alkyl, CH.sub.2 (CH.sub.2).sub.n OR", wherein R" is CH.sub.3 or (CH.sub.2).sub.n CH.sub.3 and n is 1-4, CH.sub.2 (CH.sub.2).sub.n X, wherein X is Br, Cl, or I, and n is 1-4, or (CH.sub.2).sub.n Ar, wherein Ar is unsubstituted phenyl, 3-methoxyphenyl, or 4-methoxyphenyl and n is 1 or 2, which comprises:
• a. reducing 3-bromoacetyl)-2-thiophenesulfonamide 2 to racemic 3-(2-bromo-1-hydroxyethyl)-2-thiophenesulfonamide 3 with sodium borohydride;
• b. cyclizing 3 to racemic 3,4-dihydro-2H-thieno[3,2-e]-1,2-thiazin-4-ol 1,1-dioxide 4 with sodium hydroxide;
• c. N-alkylating 4 in dimethylsulfoxide in the presence of potassium carbonate to give 3,4-dihydro-2-alkyl-2H-thieno[3,2-e]-1,2-thiazin-4-ol 1,1-dioxide 5;
• d. oxidizing 5 to 2,3-dihydro-2-alkyl-4H-thieno[3,2-e]-1,2-thiazin-4-one 1,1-dioxide 6 with sodium dichromate;
• treating 6 with boran tetrahydrofuran and a catalytic amount of (S)-tetrahydro-1-methyl-3,3-diphenyl-1H,3H-pyrrolo-[1,2-c]1,3,2 oxazaborole or (S)-tetrahydro-1,3,3-triphenyl-1H,3H-pyrrolol[1,2-c]1,3,2 oxazaborole to provide 1.