Abstract
Monocyclic thiepins have been synthesized by reaction of (4-methyl-) 3-pyrro-lidinothiophenes 1 with dimethyl acetylenedicarboxylate at − 30°C. A [2+2] cycloaddition, yielding 6,7-di(methoxycarbonyl)-(4-methyl)-5-pyrrolidino-2-thiabicyclo[3.2.0]hepta-3,6-diene 2 is followed by isomerisation into 3,4-di(methoxycarbonyl)-(6-methyl-)5-pyrrolidinothiepin 3. The predicted antiaromatic character of this class of compounds is borne out by the readiness with which they eliminate sulphur at − 30°C to give the corresponding benzene. The reaction product of dicyanoacetylene and tetramethylthiophene, recently claimed to be an unusually stable thiepin, is shown to be a 2-thiabicyclo[3.2.0]hepta-3,6-diene. Its structure allows the observed thermal rearrangement at 140°C to be interpreted as a symmetry-allowed antara,antara Cope rearrangement.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
