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Computational study of base‐induced skeletal conversion via a spirocyclic intermediate in dibenzodithiocinium derivatives by ab initio MO calculations
Author(s) -
Okada Keiji,
Tanaka Masato,
Takagi Ryukichi
Publication year - 2003
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/poc.602
Subject(s) - chemistry , heterolysis , sigmatropic reaction , ab initio , computational chemistry , ab initio quantum chemistry methods , sulfonyl , stereochemistry , derivative (finance) , basis set , rearrangement reaction , cationic polymerization , transition state , medicinal chemistry , density functional theory , molecule , organic chemistry , catalysis , alkyl , financial economics , economics
Reaction of 6‐methyl‐12‐oxo‐5 H ,7 H ‐dibenzo[ b , g ][1,5]dithiocinium salt ( 1‐SO ) with methanolic KOH afforded a mixture of dibenzothiepin derivatives 2‐SO . In order to clarify the intermediates of the rearrangement, ab initio MO calculations with the HF/6–31G * basis set were performed on the reaction intermediates, the transition states and related compounds. The rearrangement was explained in terms of the usual [2,3]‐sigmatropic shift via a spirocyclic intermediate, followed by a 1,3‐shift of the sulfonyl group. However, a different type of rearrangement was observed in 6‐methyl‐5 H ,7 H ‐dibenzo[ b , g ][1,5]dithiocinium salt ( 1‐S ), giving an unexpected dibenzothiepin derivative 3‐S along with a small amount of a ring‐opening product 8 under the same reaction conditions. The formation of 3‐S and 8 was understandable by the assumption of a cationic intermediate resulting from heterolytic cleavage at the benzyl position. Copyright © 2003 John Wiley & Sons, Ltd.