2,3-Dichloro-5,6-dicyano-1,4-benzoquinone → 2-Methylsulfanyl-thieno[2,3-h]quinazoline-8-carboxylic acid tert-butyl ester

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Reaction Steps

2-Methylsulfanyl-5,6-dihydro-thieno[2,3-h]quinazoline-8-carboxylic acid tert-butyl ester (9.0 g, 26.91 mmol) and DDQ (12.22 g, 53.82 mmol) were suspended/dissolved in dry dioxane (100 mL) and heated at reflux for 1 hour. Further DDQ (12.22 g, 53.82 mmol) was added and the resulting suspension was heated at reflux for 1.5 hours. After cooling to room temperature the mixture was concentrated under reduced pressure and then partitioned between EtOAc and saturated Na2CO3. The aqueous layer was further extracted with EtOAc (3×200 mL) and the combined organics were washed with saturated Na2CO3 (2×250 mL) and brine (1×200 mL), dried over Na2SO4, filtered and concentrated under reduced pressure. The deep brown gum obtained was redissolved in hot acetone, silica (˜60 mL) was added and the resultant suspension was concentrated under reduced pressure. The solid obtained was subjected to column chromatography (gradient elution, 20-30% acetone in hexanes, ˜600 mL silica) giving a light brown solid (6.50 g, 73% yield). ). MS (ES+) 333. δH (CDCl3) 1.7 (9H, s), 2.8 (3H, s), 7.8 (1H, d), 7.9 (1H, d), 8.8 (1H, s), 9.2 (1H, s)

Provenance & Evidence