ORTHOAMIDES .49. REACTIONS OF ORTHOAMIDE DERIVATIVES WITH SULFUR AND SELENIUM, SYNTHESES OF 1,3-THIAZOLE-DERIVATIVE AND 1,3-SELENAZOLE-DERIVATIVE

N,N-Dimethylformamide acetal reacts with elemental selenium to give a mixture of selenocarbonic acid derivatives 2 and 3, which can be conve rted to the pure N,N-dimethylcarbamidic acid Se-methylester 2 by treat ment with methyl iodide. Analogously from the orthoformic acid derivat ives 5 and 6 and selenium the N,N,N',N'-tetramethyl-selenurea 7 can be prepared. In the reaction of 12 with elemental sulfur and selenium th e amidines 14 and 15, respectively, are formed. By treatment of 14 and 15 with alpha-halogenated carbonyl compounds and triethylamine the 1, 3-thiazoles 18 and 1,3-selenazoles 19 can be prepared. The synthesis o f the propynoic acid orthoamide 26b is described. 26b reacts with the guanidinium salt 24b to give the bis-orthoamide of butynedioic acid 20 b. Other orthoamides of butynedioic acid 20b-20e can be synthesized fr om the orthoamide 20a by transamination. The thiolation of the orthoam ides affords the bis-amidinium-dithiolates 21a-c, which can be alkylat ed to give the bis-amidinium salts 27. By treatment with alpha-halogen e carbonyl compounds and triethylamine the dithiolates 21a-e are cycli zed to give thieno [3,2b] thiophenes 28a-n. The quadrupoles 21 undergo cycloadditions with dimethyl-butynedioate which afford the bis(3H-thi ophene-2 ylidenes) 29a-c. Treatment of 29a with methyl tosylate gives rise to the dithiophene 30a. The dithiophene 30b can be obtained by he ating 21b with dimethylbutynedionate.