3-Isopropoxy-4-(tri-n-butylstannyl)-3-cyclobutene-1,2-dione → HCID 86749353, compound

Participants

Reaction Steps

To a solution of 217 mg (0.50 retool) of trans-2-[2,3-dihydro-2,2-dimethyl-3-hydroxy-6-iodo-4H-1-benzopyran-4-yl]-2,3-dihydro-1H-isoindol-1-one, prepared in Example 2, and 235 mg (0.55 mmol) of 3-(1-methylethoxy)-4-(tri-n-butylstannyl)-3-cyclobutene-1,2-dione, as prepared by Liebeskind et. al. (J. Org. Chem. 55, 5359 (1990)), in DMF (620 μL) was added 23 mg (0.03 mmol) of trans-benzyl(chloro)bis(trisphenyl-phosphine) palladium (II) and 8.5 mg (0.04 mmol) of copper (I) chloride. After stirring at ambient temperature for 1.5 h, the reaction mixture was dissolved in hot CH3CN (200 mL) and was washed with hexane. The acetonitrile phase was dried over MgSO4 and was concentrated to a solid, which was then dissolved in hot THF/CH2Cl2 and absorbed onto silica gel. Purification by flash chromatography (65% EtOAc/35% hexane) gave 36 mg (16% yield) of the title compound. Additional compound was prepared in a repeat reaction in 52% yield by purifying with a short flash chromatography column using (CH3CN elution). Repeated crystallizations from CH3CN/Et2O/hexane provided an analytically pure sample, mp>250° C.: 1H-NMR (DMSO-d6 ; 400 MHz) δ7.83 (d, 1 H), 7.78 (dd, 1 H), 7.54-7.66 (m , 3 H), 7.38 (s, 1 H), 7.05 (d, 1 H), 5.86 (d, 1 It), 5.32 (br d, 1 H), 5.24 (septet, 1 H), 4.47-4.48 (br d, 1 H), 3.9-4.1 (br, 2 H), 1.51 (s, 3 H), 1.29 (s, 3 H), 1.25 (d, 3 H), and 1.02 ppm (d, 3 H); mass spectrum (DEI) m/e 447,429, 414. Anal. Calcd. for C26H25NO6. 0.5 H2O: C, 68.41; H, 5.74; N, 3.07 Found: C, 68.31; H, 5.56; N, 3.08.

Provenance & Evidence