The pyrolytic rearrangement of 1-alkynoyl-3-methylpyrazoles: synthesis of pyrazolo[1,5-a]pyridin-5-ols and related compounds was written by Brown, Roger F. C.;Eastwood, Frank W.;Fallon, Gary D.;Lee, Swee Choo;McGeary, Ross P.. And the article was included in Australian Journal of Chemistry in 1994.COA of Formula: C5H7ClN2 This article mentions the following:
Flash vacuum pyrolysis of 1-(2-alkynoyl)-3-methylpyrazoles (e.g., I; R = H, Me, Ph) at 650°/0.03 mm forms pyrazolo[1,5-a]pyridin-5-ols (e.g., II), often in high yield, which may bear substituents at C2, C3 or C7. In the absence of a 3-Me group in the precursor, N-ethynylpyrazoles are formed in low yield. The formation of both types of product is interpreted as involving 3-(N-pyrazolyl)propadienones formed by N1 → N2 migration of the N-alkynoyl group with inversion of the three-carbon chain. The fused-ring structure of 2-methylpyrazolo[1,5-a]pyridin-5-ol was established by x-ray crystallog. of the O-benzoyl derivative In the experiment, the researchers used many compounds, for example, 4-Chloro-3,5-dimethyl-1H-pyrazole (cas: 15953-73-8COA of Formula: C5H7ClN2).
4-Chloro-3,5-dimethyl-1H-pyrazole (cas: 15953-73-8) belongs to pyrazole derivatives. Pyrazole has two ring nitrogen atoms in which N1 is pyrrolic and N2 is pyridine-like. The N1 nitrogen is not reactive but is deprotonated in the presence of a base-forming anion. Protonation of pyrazole in strong acid leads to pyrazolium cations, which undergo electrophilic substitution preferentially at C3 rather than C4. The pyrazole anion is not reactive toward nucleophiles but is mostly reactive to electrophiles.COA of Formula: C5H7ClN2
Referemce:
Pyrazole – Wikipedia,
Pyrazoles – an overview | ScienceDirect Topics