Squaric acid → HCID 10935546, compound

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Reaction Steps

This Example illustrates the preparation, by a reaction analogous to D→E shown in FIG. 1, of the squaric acid derivative of Formula II in which Q1 is a 2,6-bis(1,1-dimethylethyl)-4-pyrylidene grouping and R1 is a hydrogen atom. 3-[2,6-Bis(1,1-dimethylethyl)-(4H-pyran-4-ylidene)-methyl]-2,4,4-tri-chlorocyclobut-2-en-1-one (100 mg, 0.27 mmole, prepared in Example 47 above), was dissolved in triflic acid (1 mL) and the resultant solution heated at 60° C. for 1 hour, 80° C. for a further 2 hours, and finally at 105° C. for 5 hours. The hot mixture was then poured over ice, and the resultant mixture stirred to give a solid precipitate. The mixture was extracted several times with dichloromethane, and the extracts were combined, washed with brine, dried over sodium sulfate and evaporated to dryness. The residue was redissolved in dichloromethane and applied to two preparative silica gel chromatography plates. Elution with 8% methanol in dichloromethane resulted in the development of many minor bands, with a major yellow band streaking from the origin. The major yellow band was extracted with methanol, the resultant solution evaporated to dryness, the residue dissolved in dichloromethane, and the solution filtered and evaporated to dryness. Pumping under high vacuum gave a yellow-brown solid (70 mg, 87% yield). The structure of the product was confirmed by proton NMR spectroscopy.

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