Preparation of alpha-diazocarbonyl compounds from beta-lapachone derivatives and other 1,2-naphthoquinones: use of the 2D NMR 1H,15N and 1H,13C HMBC techniques in assigning regiochemistry.
The assignment of the diazo site in products of the reaction of p-toluenesulfonylhydrazine with beta-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 1H,13C HMBC and 1H,15N 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 beta-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-2,3,4,6-tetrahydro-2H-benzo[h]cromen-5-one, obtained from beta-lapachone, was achieved using single crystal X-ray diffraction.
Universidade Federal Fluminense; Instituto de Química, Departamento de Química Orgânica, 24020-150 Niterói, Rio de Janeiro, Brazil. cegvito@vm.uff.br
Vitor F
VF
Ferreira
Alessandra
A
Jorqueira
Kátia Z
KZ
Leal
Hélio R X
HR
Pimentel
Peter R
PR
Seidl
Milton N
MN
da Silva
Maria C B V
MC
da Souza
Antonio V
AV
Pinto
James L
JL
Wardell
Solange M S V
SM
Wardell
D002247:Carbon Isotopes; D003979:Diazonium Compounds / Q000032:analysis / Q000138:chemical synthesis*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D015394:Molecular Structure; D009285:Naphthoquinones / Q000737:chemistry*; D009587:Nitrogen Isotopes; D011522:Protons; D013237:Stereoisomerism; D014961:X-Ray Diffraction
D002247:Carbon Isotopes; D003979:Diazonium Compounds; D009285:Naphthoquinones; D009587:Nitrogen Isotopes; D011522:Protons; C014638:beta-lapachone