Preparation of α-diazocarbonyl compounds from β-lapachone derivatives and other 1,2-naphthoquinones: use of the 2D NMR 1H,15N and 1H,13C HMBC techniques in assigning regiochemistry

✍ Scribed by Vitor F. Ferreira; Alessandra Jorqueira; Kátia Z. Leal; Hélio R. X. Pimentel; Peter R. Seidl; Milton N. da Silva; Maria C. B. V. da Souza; Antonio V. Pinto; James L. Wardell; Solange M. S. V. Wardell

• Publisher: John Wiley and Sons
• Year: 2006
• Tongue: English
• Weight: 291 KB
• Volume: 44
• Category: Article
• ISSN: 0749-1581
• DOI: 10.1002/mrc.1778

✦ Synopsis

The assignment of the diazo site in products of the reaction of p-toluenesulfonylhydrazine with b-lapachone, 3,4-dihydro-2,2-dimethyl-2H-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 b-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(2H)-naphthalenone, an additional product isolated from the reaction of p-toluenesulfonylhydrazide with 1,2-naphthoquinone was 2-diazo-4-hydroxy-1(2H)-naphthalenone. Confirmation of the formation of 6-diazo-2,2-dimethyl-2,3,4,6tetrahydro-2H-benzo[h]cromen-5-one, obtained from b-lapachone, was achieved using single crystal X-ray diffraction.