Selective acetylation of methylhydrazine. 1-Acetyl-1-methyl- and 1-acetyl-2-methylhydrazine

Synthesis of Spiro-Fused Pyrazolidoylisoxazolines

“…In contrast, hydrazinolysis of methyl pyrazine-2-carboxylate ( 18 ; Scheme 4) delivered N’ -methylpyrazine-2-carbohydrazide ( 19 ) in excellent yield (90%). 10 The divergent regioselectivities observed with these two methods can be rationalized on the basis of the mechanistic differences described by Condon et al : 11 acylation using an anhydride is governed by the greater nucleophilicity of the substituted nitrogen whereas acylation using a simple ester is governed by steric congestion around the neutral, tetrahedral intermediate. 11 With hydrazide 19 in hand, the methods employed in Scheme 2 and 3 delivered the targeted pyrazolidine and the sequence-ending 1,3-dipolar cycloaddition delivered final product 20 in 55% yield.…”

Comparison of the Electrophilic Reactivities of N‐Acylpyridinium Ions and Other Acylating Agents

“…Whereas several anhydrides, including benzoic anhydride (2) and acetic anhydride (3), were found to react with methylhydrazine (28) selectively at the NHMe group, the corresponding reactions with ethyl acetate occurred at the NH 2 group predominantly (Scheme 2). [8] Hinman and Fulton further observed that the selectivity for NH 2 attack of methylhydrazine (28) in reactions with esters increased with increasing size of the acyl group, that is, the percentage of 1-acyl-1-methylhydrazine decreased in the order: methyl acetate Ͼ methyl propionate Ͼ methyl isobutyrate. [8] Hinman and Fulton further observed that the selectivity for NH 2 attack of methylhydrazine (28) in reactions with esters increased with increasing size of the acyl group, that is, the percentage of 1-acyl-1-methylhydrazine decreased in the order: methyl acetate Ͼ methyl propionate Ͼ methyl isobutyrate.…”

“…[11] However, the situation is more complicated in acylation reactions. [8,9] Nucleophilic displacement of the B Ac 2 type with rate-determining addition was claimed for the reaction of 28 with acetic anhydride, whereas the corresponding reaction with ethyl acetate was claimed to proceed through addition-elimination with rate-limiting proton transfer. [8,9] Nucleophilic displacement of the B Ac 2 type with rate-determining addition was claimed for the reaction of 28 with acetic anhydride, whereas the corresponding reaction with ethyl acetate was claimed to proceed through addition-elimination with rate-limiting proton transfer.…”

“…[9] Scheme 2. [8] The combination of 4-nitrophenyl benzoate (1) with two equivalents of potassium diethyl malonate (7) in dimethyl sulfoxide (DMSO) at 20°C yielded 31 after workup with 4-toluenesulfonic acid, that is, 1 reacted with nucleophilic replacement of 4-nitrophenolate by the carbanion (Scheme 3). [8] The combination of 4-nitrophenyl benzoate (1) with two equivalents of potassium diethyl malonate (7) in dimethyl sulfoxide (DMSO) at 20°C yielded 31 after workup with 4-toluenesulfonic acid, that is, 1 reacted with nucleophilic replacement of 4-nitrophenolate by the carbanion (Scheme 3).…”

Development of Analytical Techniques for Toxicokinetic Research

“…"* l-acetyl-2-methylhydrazine was prepared (Condon, 1972) by the reaction of excess ethyl acetate with MMH.…”