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1,3-Dipolar Cycloadditions, 96. – Cycloadditions of Alicyclic ThioneS-Oxides with Alicyclic Thiones

✍ Scribed by Huisgen, Rolf ;Mloston, Grzegorz ;Polborn, Kurt ;Sustmann, Reiner ;Sicking, Willi

Publisher
John Wiley and Sons
Year
1997
Tongue
English
Weight
708 KB
Volume
1997
Category
Article
ISSN
0947-3440

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✦ Synopsis

Abstract

Thione S‐oxides (sulfines) harbor the allyl anion MO of 1,3‐dipoles, but fail to undergo 1,3‐cycloadditions to the usual dipolarophiles with a CC multiple bond. Thioketones stand the test as superdipolarophiles. The thione S‐oxides 3 and 9 combined with the thioketones 5 and 7 at 80–100°C, furnishing spiro‐1,2,4‐oxadithiolanes in high yields despite steric hindrance. The structures of the cycloadducts were clarified by their spectra and an X‐ray analysis of 11. Becke3LYP/6‐31G* calculations of transition structures and products for the cycloadditions of thioformaldehyde S‐oxide to thioformaldehyde support the observed regiochemistry. The activation energy amounts to 3.9 kcal mol^−1^, in contrast to E~A~ = 17.4 kcal mol^−1^ for the corresponding addition to ethylene. The transition structures are in accordance with concerted cycloadditions.

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