Substituted 3,4-pyridynes: clean cycloadditions
Citation:
S. J. Connon and A. F. Hegarty, Substituted 3,4-pyridynes: clean cycloadditions, Journal of the Chemical Society, Perkin Transactions 1, 1, 8, 2000, 1245, 1249Download Item:
Abstract:
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 tert-butyllithium at low temperatures, followed by elimination of lithium chloride affords 2- and 6-alkoxy-3,4-pyridynes. These species are trapped in 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 ?-lithiation by tert-butyllithium because of its increased steric bulk.
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http://people.tcd.ie/connonsDescription:
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Author: CONNON, STEPHEN
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Royal Society of ChemistryType of material:
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Journal of the Chemical Society, Perkin Transactions 1;1;
8;
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