TY - JOUR
T1 - Synthesis of spiro-fused (C5)-isoxazolino-(C4)-pyrazolones (1-Oxa-2,7,8-triazaspiro[4,4]-2,8-dien-6-ones) via 1,3-dipolar cycloaddition and cycloelimination
AU - Sammelson, Robert E.
AU - Gurusinghe, Chamindra D.
AU - Kurth, Jeffrey M.
AU - Olmstead, Marilyn M.
AU - Kurth, Mark J.
PY - 2002/2/8
Y1 - 2002/2/8
N2 - An efficient and selective method for the synthesis of spiro-fused (C5)-isoxazolino-(C4)-pyrazolones (C) is reported. The process consists of utilizing the Baylis - Hillman reaction - or a quicker, stepwise MAC procedure - to give I followed by 1,3-dipolar cycloaddition and Swern oxidation to give β-ketoesters H, which were condensed with hydrazine derivatives to provide hydrazones that underwent cycloelimination. These novel spiro-fused (C5)-isoxazolino-(C4)-pyrazolones were confirmed by spectroscopic analysis as well as single-crystal X-ray of 5. We also concluded that all condensations/cycloeliminations, except with hydrazine itself, were more effective with catalysts or higher reaction temperatures. For example, TiCl4 was an efficient catalyst for hydrazone formation and cycloelimination with methylhydrazine, while phenyl-, benzyl-, and (4-methoxyphenyl)hydrazine reacted effectively without catalyst in refiuxing xylene.
AB - An efficient and selective method for the synthesis of spiro-fused (C5)-isoxazolino-(C4)-pyrazolones (C) is reported. The process consists of utilizing the Baylis - Hillman reaction - or a quicker, stepwise MAC procedure - to give I followed by 1,3-dipolar cycloaddition and Swern oxidation to give β-ketoesters H, which were condensed with hydrazine derivatives to provide hydrazones that underwent cycloelimination. These novel spiro-fused (C5)-isoxazolino-(C4)-pyrazolones were confirmed by spectroscopic analysis as well as single-crystal X-ray of 5. We also concluded that all condensations/cycloeliminations, except with hydrazine itself, were more effective with catalysts or higher reaction temperatures. For example, TiCl4 was an efficient catalyst for hydrazone formation and cycloelimination with methylhydrazine, while phenyl-, benzyl-, and (4-methoxyphenyl)hydrazine reacted effectively without catalyst in refiuxing xylene.
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U2 - 10.1021/jo010895d
DO - 10.1021/jo010895d
M3 - Article
C2 - 11856032
AN - SCOPUS:0037039909
VL - 67
SP - 876
EP - 882
JO - Journal of Organic Chemistry
JF - Journal of Organic Chemistry
SN - 0022-3263
IS - 3
ER -