Electrophilic substitution in naphthalenes: cyclisation of naphthylbutanols to tetrahydrophenanthrene
- 1 January 1981
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in Journal of the Chemical Society, Perkin Transactions 2
- No. 2,p. 286-297
- https://doi.org/10.1039/p29810000286
Abstract
Both 4-(1-naphthyl)butanol and 4-(2-naphthyl)butanol cyclised in refluxing boron trifluoride–ether to give 1,2,3,4-tetrahydrophenanthrene. By use of the corresponding, 1,1-dideuteriobutanol derivatives and analysis of the products by 220 MHz 1H n.m.r. spectroscopy it has been demonstrated that the 1-naphthylbutanol cyclises by two distinct pathways, (a) by direct attack (84%) at the 2-position, and (b) by ipso-attack (16%) at the 1-position of the naphthalene nucleus, followed by rearrangement. The 2-naphthylbutanol cyclises exclusively by direct substitution at the 1-position. With 4-(4-methoxy-1-naphthyl)-1,1-dideuteriobutanol on the other hand the proportion of ipso-substitution rises to 71% as shown by the 360 MHz 1H n.m.r. spectra of the resulting mixture of tetrahydrophenanthrenes.Keywords
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