Alkynyl propargyl sulfides underwent [3,3] sigmatropic rearrangement followed by ring closure to afford isolable 4-methylenecyclobutenethiones, and an intermediary allenylthioketene 2 was isolated by heating t-butyldimethylsilylethynyl propargyl sulfide.

Cyclobutane derivatives Q 0022Isolation and Characterization of an Allenylthioketene and 4-Methylenecyclobutenethiones Generated by Thermal Reaction of Alkynyl Propargyl Sulfides.-Alkynyl propargyl sulfides (I) undergo thermally induced [3,3] sigmatropic rearrangement followed by ring closure to afford 4-methylenecyclobutenethiones (III). Similar thermal reaction of alkynyl propargyl sulfide (VII) stops at the formation of relatively stable allenylthioketone (VIII). Studies on the reactivity of both types of reaction products round off the report. -(AOYAGI*, S.; SUGIMURA, K.; KANNO, N.; WATANABE, D.; SHIMADA, K.; TAKIKAWA, Y.; Chem. Lett. 35 (2006) 9, 992-993; Dep. Chem. Eng., Fac. Eng., Iwate Univ., Ueda, Morioka 020, Japan; Eng.) -R. Langenstrassen 05-059