REACTIVITY IN ELIMINATIVE CLEAVAGE OF ACTIVATED 4-MEMBERED RINGS - THE BEHAVIOR OF 3-HYDROXYTHIETANE DERIVATIVES

3-Hydroxythietane derivatives undergo retro-aldol ring fission in aque ous sodium hydroxide at a rate determined by the substituent (H or Ph) at the 3 position and by the oxidation state of sulfur, Reactions occ ur between 4 x 10(4) and 5 x 10(5) times faster than for the open chai n analogues, These rate accelerations correlate with an expression of strain energy between 41% and 33% compared with approximately 26% for alkene-forming eliminations of cyclobutanes, These differences, togeth er with the differences in relative sensitivities to alpha-phenyl subs titution and uniformly positive values of entropies of activation for 3-hydroxythietane derivatives, suggest a greater degree of ring cleava ge in the transition structure for thietanes than for cyclobutanes, Ri ng fission is, however, accompanied by concomitant protonation of the leaving carbon group as evidenced by the isotope discrimination value of 1.7 for reaction of 3e. 3-Hydroxythietane itself does not undergo r etro-aldol ring cleavage but rather anionic polymerisation to yield po lymer 9a.