3,4-Diisopropoxy-3-cyclobutene-1,2-dione → HCID 19955586, compound

Participants

Reaction Conditions

Reaction Steps

To a solution of 2-bromo-4'-methylbiphenyl (9.0 g; obtainable as described in Example 3 (a) and in Gomberg and Pernert, J. Am. Chem. Soc. (1926) Vol 48 p 1373) in tetrahydrofuran (60 ml) was added butyllithium (2.5M in hexanes, 15.3 ml) dropwise at -70° C. under a nitrogen atmosphere over a period of 3 minutes. The mixture was stirred for 10 minutes at -70° C. then added to a solution of 3,4-diisopropoxycyclobut-3-ene-1,2-dione (7.6 g) in tetrahydrofuran (100 ml) at -70° C. under nitrogen over a period of 1 minute. The solution obtained was stirred for an additional 30 minutes at -70° C. then quenched with trifluoroacetic anhydride (6.4 ml), followed by saturated aqueous ammonium chloride (40 ml). The resulting mixture was allowed to warm to ambient temperature, then partitioned between diethyl ether (300 ml) and aqueous sodium bicarbonate (5%, 300 ml). The aqueous layer was re-extracted with diethyl ether (200 ml) and the combined organic layers were washed with brine, dried over magnesium sulphate, and evaporated to give a yellow oily solid which was purified by flash chromatography on silica gel (eluting with 10% rising to 20% ethyl acetate in petroleum ether (b.p. 60°-80° C.)) to give the intermediate compound 3-isopropoxy-4-(4'-methylbiphenyl-2-yl)cyclobut-3-ene-1,2-dione as a yellow solid (6.7 g), substantially identical to the product of Example 1(b). The above method is described in Reed et al, Journal of Organic Chemistry (1988) Vol.53, p 2477.

Provenance & Evidence