Squaric acid → HCID 18402114, compound

Participants

Reaction Conditions

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-thiopyrylidene grouping and R1 is ahydrogen atom. 3-[2,6-Bis(1,1-dimethylethyl)-(4H-thiopyran-4-ylidene)methyl]-2,4,4-trichlorocyclobut-2-en-1-one (279 mg, 0.59 mmole, prepared in Example 51 above) was added to a solution of trifluoromethane sulfonic acid (1.0 mL) in water (35 mg). The colorless reaction mixture was stirred under nitrogen with heating to 90° C. for 5 hours, after which it was cooled to 20° C. and stirred for 12 hours at that temperature. The reaction mixture was quenched into ice/water (15 mL) dropwise, with efficient agitation. A brown precipitate formed which was initially crystalline, but become gummy after standing for several minutes. This was separated by filtration, washed with dilute aqueous sodium sulfate, and separated into two portions. One portion was dried, to give a red-brown amorphous solid (110 mg). The second portion was partly purified by flash chromatography on silica gel with 10-16-20 % methanol/dichloromethane as eluent to yield a still impure product (55 mg, exhibiting, inter alia, mle 363 in the mass spectrum), which was used directly in Example 70 without further purification.

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