Tetrahedron Letters. Vol. 33. No. 29, pp. 4123-4126,1992 Rimed in Cm* Britain ... FACILE FORMATIONS OF KETALS OF a, a-DIHALOACETOPHENONES ... Pakorn Bovonsombat and Edward McNelis* Department of Chemistry, New York University, New York, New York 10003 ... Recently our attention has been turned to the uses of N-iodosuccinimide (NIS, l-iodo-2,5-pyrrolidinedione ) and catalytic amounts of acidic materials such as (hydroxy(tosyloxy)iodo)benzene