Regioselectivity in the formation of cyclic sulphones from 4- and 5-alkenesulphonyl chlorides

✍ Scribed by Peter N. Culshaw; John C. Walton

• Book ID: 104228378
• Publisher: Elsevier Science
• Year: 1990
• Tongue: French
• Weight: 235 KB
• Volume: 31
• Category: Article
• ISSN: 0040-4039
• DOI: 10.1016/s0040-4039(00)97084-9

✦ Synopsis

Alk4enesulphonyl chlorides and alk-5enesulphonyl chlorides cyclise under free radical conditions mainly in the & mode to give tetrahydrothiopyran-1 , l-dioxide and thiepane-1, ldioxide respectively. Sulphonyl radicals, RS02'. generated from sulphonyl chlorides, readily undergo intermolecular addition to alkenes to give sulphones. 1-3 However, the intramolecular cyclisation reaction, which is a potential route to cyclic B-chloro sulphones, has scarcely been investigated.

Unsaturated

sulphonyl radicals were proposed as intermediates in the reactions of pentenylcobaloximes with trichlotomethanesulphonyl chloride4 and sulphur dioxide.5 Cyclisation in the & mode to give six-membered ring tetrahydrothiopyran-1, l-dioxides was observed.

We generated the archetype pentenesulphonyl radical 2 by treatment of pent4enesulphonyl chloride, 1, with photochemically produced trimethyltin radicals, in the cavity of an EPR spectrometer. Radical 2 was observed in the temperature range 240-370 K but no cyclised species were detected at higher temperatures.