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Condition-dependent transformation of α-thioiminium salts derived from α-bromoamides and thioamides
Authors: Marek Lukáš | Váňa Jiří | Hanusek Jiří
Year: 2022
Type of publication: ostatní - přednáška nebo poster
Page from-to: nestránkováno
Titles:
Language Name Abstract Keywords
eng Condition-dependent transformation of α-thioiminium salts derived from α-bromoamides and thioamides Recently, we have discovered the Eschenmoser reaction of α-bromooxindole with various thiobenzamides, which proceeds atypically without the assistance of thiophile and even the base. Therefore, we decided to investigate the reactivity of structurally similar α-bromoamides/α-bromolactams. For this purpose, a number of α-brominated (a)cyclic substrates 1a-b, 2 were synthesized. Upon the reaction of six-membered (1a,b) representatives with thiobenzamides (R = H) and thiobenzanilides (R = Ar), several novel 1,2-dihydroisoquinolin-3(4H)-one (3) and isoquinoline-1,3(2H,4H)-dione (4) derivatives were formed. Reaction of 1,1-dimethyl-1,2-dihydroisoquinolin-3(4H)-one (1a) with primary thiobenzamides gave fluorescent tricyclic thiazoles (5) when highly polar aprotic ACN or DMF were used as solvents. Attempts to achieve sulfide contraction by the addition of a thiophile (trimethyl-phosphite) resulted in the formation of an N-methylated analogue (6). Finally, the expected course of the Eschenmoser reaction was achieved using a mild base (KHCO3) and solvent with lower polarity (DCM). On the contrary, the reaction of 2-bromophenylacetamide derivatives (2) gave only 2,5-diarylthiazole (7) as a product and the formation of vinylogous amines did not take place at all. Analogous thiazolium salts (8) were formed from secondary acyclic α-bromoamides (R’ = H, R’’ = Me). In all cases, observed reactivity was consistent with DFT (B3LYP/6-311++g(d p) calculations. α-bromoamides; thioamides; Eschenmoser reaction; cyclization

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