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Preparation of α‐diazocarbonyl compounds from β‐lapachone derivatives and other 1,2‐naphthoquinones: use of the 2D NMR 1 H, 15 N and 1 H, 13 C HMBC techniques in assigning regiochemistry
Author(s) -
Ferreira Vitor F.,
Jorqueira Alessandra,
Leal Kátia Z.,
Pimentel Hélio R. X.,
Seidl Peter R.,
da Silva Milton N.,
da Souza Maria C. B. V.,
Pinto Antonio V.,
Wardell James L.,
Wardell Solange M. S. V.
Publication year - 2006
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/mrc.1778
Subject(s) - chemistry , diazo , carbon 13 nmr , regioselectivity , naphthoquinone , steric effects , stereochemistry , methanol , quinone , medicinal chemistry , organic chemistry , catalysis
The assignment of the diazo site in products of the reaction of p ‐toluenesulfonylhydrazine with β‐lapachone, 3,4‐dihydro‐2,2‐dimethyl‐2 H ‐naphtho[1,2‐b]pyran‐5,6‐dione, and other 1,2‐naphthoquinones in methanol solution at room temperature has been accomplished using 1 H, 13 C HMBC and 1 H, 15 N HMBC NMR experiments. Only one diazo‐naphthalenone product was isolated in yields ranging from 50–100% from each reaction. The site of diazo substitution of β‐lapachone and derivatives is the 1‐position, in contrast to substitution at the 2‐position in 4‐MeO‐1,2‐naphthoquinone. Steric factors, rather than electronic factors, control the reaction site. Along with 2‐diazo‐1(2 H )‐naphthalenone, an additional product isolated from the reaction of p ‐toluenesulfonylhydrazide with 1,2‐naphthoquinone was 2‐diazo‐4‐hydroxy‐1(2 H )‐naphthalenone. Confirmation of the formation of 6‐diazo‐2,2‐dimethyl‐2,3,4,6‐tetrahydro‐2 H ‐benzo[h]cromen‐5‐one, obtained from β‐lapachone, was achieved using single crystal X‐ray diffraction. Copyright © 2006 John Wiley & Sons, Ltd.