- Rhodium-catalysed nucleophilic ring opening reaction of 1- and 3-ethoxy-5,8-epoxy-5,8-dihydroisoquinolines
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2-Ethoxy-3- and 5-chloropyridines were obtained from 2,3- and 2,5-dichloropyridine. Reaction of 2,3- and 2,5-dichloropyridines with tBuLi in the presence of furan gave 1- and 3-ethoxy-5,8-epoxy-5,8-dihydroisoquinolines. The rhodium-catalysed ring-opening
- Kelebekli, Latif
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- Substituted 3,4-pyridynes: Clean cycloadditions
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The stabilisation of 3,4-pyridyne (1) by an alkoxy group adjacent to the ring nitrogen is reported. The regioselective lithiation of 2-ethoxy- (14), 2-methoxy- (18), 2-isopropoxy- (19) and 6-isopropoxy- (26) -3-chloropyridines with tertbutyllithium at low temperatures, followed by elimination of lithium chloride affords 2- and 6-alkoxy-3,4-pyridynes. These species are trapped m situ with furan in a Diels-Alder reaction to give 5-8 in 66-89% yield, and do not give products typical of polymerisation or nucleophilic addition to the 3,4-pyridyne intermediates. As a comparison treatment of 3-chloropyridine with furan and LDA gives only 19% of adduct (4). We also report the novel use of the isopropoxy (rather than methoxy) group in these systems, which can act as a heteroatomic electron donating group which inhibits a-lithiation by tert-butyllithium because of its increased steric bulk. The Royal Society of Chemistry 2000.
- Connon, Stephen J.,Hegarty, Anthony F.
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p. 1245 - 1249
(2007/10/03)
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