Acetamides, Michael addition

A series of 2-(thiazol-5-yl)acetamides and acetates 35a/b has been prepared in one pot from the reactions of benzotriazolylthione derivatives 32 with A,A-dimethyl-4-A ,A -bis(trimethylsilyl)aminobut-2-yne amide 31a and ethyl 4-A,A-bis(trimethylsilyl)aminobut-2-ynoate 31b, respectively <06TL8661>. Presumably, the initial adducts 33a/b undergo intramolecular thia-Michael addition to give 34a/b, which isomerize to thiazoles 35a/b. 

Starting material for the synthesis is the enaminoaldehyde obtainable by some version of the Villsmeyer reaction on pi coline derivative 9. Condensation of that with cyanoacetamide in the presence of methoxide leads to pyridone J. The reaction can be rationalized by assuming that the initial step consists in Michael addition of the anion from acetamide to the acrolein elimination of dimethyl amine would afford the intermediate Conden-... 

Silica-supported Lewis acids are useful catalysts with microwave irradiation for conjugate additions. The silica-supported catalysts are obtained by treatment of silica with ZnCh [Si(Zn)], Et2AlCl [Si(Al)] or TiCl4 [Si(Ti)] [ 150-152], The Michael addition of methyl a-acetamidoacrylate (196) with indole (2) under Si(M) heterogeneous catalysis assisted by microwave irradiation afforded the alanine derivative 197 within 15 min and/or bis-indolyl 198, depending on the reaction conditions (Scheme 45) [153]. While the bis-indolyl product 198 is only formed when Si(Zn) was used as catalyst, the alanine derivative 197, as a single product is formed under thermal heating in a yield of 12%. The best yields were observed with Si(Al) (Table 5). The product 198 was obtained by elimination of acetamide followed by a-Michael addition between intermediate 199 with a second mole of indole. 

A new preparation " of the diamine (7), by Michael addition of dimethyl-acetamide to 2,5-dimethoxy-co-nitrostyrene followed by reduction of the adduct, constitutes a new synthesis of bufotenine (Scheme 1), since the amine (7) has already been converted into bufotenine. 

Nitroalkene acceptors A regioselective aminobromination of / -nitrostyrenes ArCH=CHN02 with acetamide and NBS in acetone, catalysed by K3PO4, has been reported to produce the vicinal haloamides. A plausible mechanism involving an initial Michael addition was proposed, which appears to be more likely than that " criticized by this reviewer in the previous paragraph. 

Azaarylacetates and acetamides, such as (399), have been reported to undergo Michael additions to nitroalkenes (394) in the presence of the nickel(II)-bis(diamine) complex 0 (401) and molecular sieves to produce (400) with >19 dr and <99% ee 0... 

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