Ethyl thioxoacetate

The groups of Kirby224,340 and of Revesz477 have studied the Diels-Alder reactions of thebaine 134 with ethyl thioxoacetate (equation 140) and other thioaldehydes, thus preparing several opiate antagonists. 

Lown et al. reported a simple retro [2 + 2] fragmentation of oxathietane (33) [prepared from tetramethylaziridine (32)] in aqueous medium, followed by trapping of thioacetone with anthracene (86JA3811,86JOC2116). Lee et al. trapped ethyl thioxoacetate from retro Diels-Alder fragmentation of a bicyclic precursor (35), which was prepared in a fascinating reaction from the aminocrotonate (34) and sulfur dichloride (85JOC3216). 

One such method shown in Eq. (6)19 makes use of a fragmentation of phthalimide derivative 4 to generate ethyl thioxoacetate. 

Y. Watanabe and T. Sakakibara, Tetrahedron, 65, 599-606 (2009). Draw a reaction showing the conversion of ethyl thioxoacetate to the thiine. 

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