D. Geffken et G. Groll, CYCLOCONDENSATION OF 2-(3-THIENYL)SUBSTIT UTED O-ALKYL GLYCOLOHYDROXAMIC ACIDS TO 5,6-DIHYDRO-6AH-THIENO[2,3-B]PYRROL-5-ONES, Die Pharmazie, 48(11), 1993, pp. 801-806
Dicyclohexylcarbodiimide converts the O-alkyl glycolohydroxamic acids
4A, 4B into 5,6-dihydro-6aH-thie-no[2,3-b]pyrrol-5-ones 6A, 6B, the fo
rmation of which depends on the nature of the C2-substituents. Acid-ca
talyzed methanolysis of 6Ba, c, e affords the cyclic hydroxamic acids
9a-c that can be reduced by titanium chloride to 8. Addition of phenyl
isocyanate to 9a gives smoothly 10 and compound 11 arises from alkylat
ion of 9b with tert-butyl bromoacetate.