Apr-May 1991 Substituent Interaction with Ring Sulfur in some Heterocyclic Compounds David M. McKinnon* and AA Abouzeid Chemistry Dept., University of Manitoba, Winnipeg, Manitoba Canada R3T 2N2 Received October 30, 1990 The infrared carbonyl absorptions of 7-acetyl-l,2-benzisothiazoles are similar to 7-acetylbenzo[6]thio- phenes, but are lower by approximately 15 cm"1 than the corresponding benzo[£>]furans. The reasons for this are discussed. 749 ...