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Ring‐Opening/Ring‐Closing Protocols from Nitrothiophenes: Six‐Membered versus Unusual Eight‐Membered Sulfur Heterocycles through Michael‐Type Addition on Nitrobutadienes
Author(s) -
Bianchi Lara,
Giorgi Gianluca,
Maccagno Massimo,
Petrillo Giovanni,
Sancassan Fernando,
Severi Elda,
Spinelli Domenico,
Stenta Marco,
Tavani Cinzia
Publication year - 2010
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200902528
Subject(s) - ring (chemistry) , thiopyran , moiety , sulfur , chemistry , aromaticity , stereochemistry , molecule , organic chemistry
When Ar is a low‐aromaticity homo‐ or heterosystem, the sulfonyl‐stabilized anion of nitrobutadienes 4 (which derive from the initial ring opening of 3‐nitrothiophene) undergoes a rather surprising addition onto the aromatic ring itself, thereby leading to the construction of an unusual eight‐membered sulfur heterocycle condensed with the original Ar ring. The competitiveness of such a pathway with respect to the formation of the thiopyran ring (i.e., addition onto the nitrovinyl moiety) is favored at low temperatures, thus revealing its nature as a kinetically controlled process.