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Reductive Elimination of Phenylsulfonyl Groups in the 3-Position of Benzo[a]heptalene-2,4-diols

✍ Scribed by Mohy eldin Abdel Fattah; Samir El Rayes; El Sayed Ahmed Soliman; Anthony Linden; Khaled Abou-Hadeed; Hans-Jürgen Hansen

Publisher
John Wiley and Sons
Year
2005
Tongue
German
Weight
367 KB
Volume
88
Category
Article
ISSN
0018-019X

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✦ Synopsis

Abstract

3‐(Phenylsulfonyl)benzo[a]heptalene‐2,4‐diols 1 can be desulfonylated with an excess of LiAlH~4~/MeLi⋅LiBr in boiling THF in good yields (Scheme 6). When the reaction is run with LiAlH~4~/MeLi, mainly the 3,3′‐disulfides 6 of the corresponding 2,4‐dihydroxybenzo[a]heptalene‐3‐thiols are formed after workup (Scheme 7). However, the best yields of desulfonylated products are obtained when the 2,4‐dimethoxy‐substituted benzo[a]heptalenes 2 are reduced with an excess of LiAlH~4~/TiCl~4~ at −78→20° in THF (Scheme 10). Attempts to substitute the PhSO~2~ group of 2 with freshly prepared MeONa in boiling THF led to a highly selective ether cleavage of the 4‐MeO group, rather than to desulfonylation (Scheme 13).

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