RATES OF SN2' AND SNI' REARRANGEMENTS IN 3-(ALPHA-HALOALKYL)BENZO[BETA]THIOPHENE 1,1-DIOXIDES

Rate constants have been determined for the reactions of 3-(±-chloroethyl)- and 3-(±-chloro-±-methylethyl)-benzo[b]thiophene 1,1-dioxides (1a and 1b, respectively) with piperidine in benzene. For 1a the rate of (enamine) product formation (spectrophotometric rate) is slower than the rate of chloride release (titrimetric rate) indicating that the SNi′ type of rearrangement is rate determining. This kinetic analysis predicts formation of an intermediate, and evidence is presented to show that such is formed. For 1b the rate of (enamine) product formation is equal to the rate of halide release indicating that in this instance the Sn2′ step, rather than the SNi′ step, is rate determining. © 1968, American Chemical Society. All rights reserved.