Abstract
A convenient, three-step synthesis of benz[a ]acephenanthrene (6 ) from commercially available materials
is described.
Key words
Wittig reaction - photocyclization - benz[a ]acephenantrene
References
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6 A solution of NaOEt in EtOH (12 mmol
of Na in 50 mL EtOH) was added slowly to a boiling solution of the benzyltriphenylphosphonium
bromide (10 mmol) and 4 (1.82 g; 10 mmol)
dissolved in 10 mL of EtOH/benzene (1:1). The mixture was
refluxed for 1 h and then kept at room temperature overnight (stirring).
The product was purified by column chromatography with hexane to
give 1.38 g (54%) of cis and trans isomers of 5 (M+ 256);
separation of the mixture was not attempted.
7 A solution of 5 (0.512
g, 2 mmol) and 30 mg of iodine in cyclohexane (300 mL) was irradiated
with a 200 W high pressure quartz Hg-vapor lamp for 2 h. Evaporation
of the solvent provided a single product (by NMR and GC/MS) which
was purified by column chromatography with hexane to give 0.42 g
(83%) of a pale yellow solid 6 :
mp 118-120 °C (lit.
[4 1 H
NMR (300 MHz, CDCl3 ) δ 9.25 (d, J = , 8.4 Hz, 2 H), 7.98 (d, J = 7.8 Hz, 2 H), 7.71 (s, 2
H), 7.68-7.64 (m, 4 H), 3.45 (s, 4 H); 13 C
NMR (75.4 MHz, CDCl3 ) δ 143.4, 137.89, 135.77,
129.75, 129.27, 127.06, 125.87, 125.7, 124.89, 121.87, 29.90; MS
(EI, 70 eV) m/z (rel. intensity)
254 (100).
