Iodocyclization of Hydroxylamine Derivatives Based on the Control of Oxidative Aromatization Leading to 2,5-Dihydroisoxazoles and Isoxazoles
摘要:
An efficient method for the synthesis of 2,5-dihydroisoxazoles and isoxazoles using iodocyclization of N-alkoxycarbonyl O-propargylic hydroxylamines has been developed. 2,5-Dihydro-4-iodoisoxazole underwent the cross-coupling reactions without aromatization to afford polyfunctionalized 2,5-dihydroisoxazoles. This process was applied to the preparation of valdecoxib and its 2,5-dihydro-derivative.
Iodocyclization of Hydroxylamine Derivatives Based on the Control of Oxidative Aromatization Leading to 2,5-Dihydroisoxazoles and Isoxazoles
摘要:
An efficient method for the synthesis of 2,5-dihydroisoxazoles and isoxazoles using iodocyclization of N-alkoxycarbonyl O-propargylic hydroxylamines has been developed. 2,5-Dihydro-4-iodoisoxazole underwent the cross-coupling reactions without aromatization to afford polyfunctionalized 2,5-dihydroisoxazoles. This process was applied to the preparation of valdecoxib and its 2,5-dihydro-derivative.
Borylative Cyclization of 1,6-Allenynes Driven by BCl<sub>3</sub>
作者:Chun-Hua Yang、Xiangkun Sun、Congcong Niu、Zhiwei Zhang、Mingzhu Liu、Fangjie Zheng、Ling Jiang、Xiangtao Kong、Zhantao Yang
DOI:10.1021/acs.orglett.1c03062
日期:2021.10.15
A metal-free intramolecular borylative cyclization of 1,6-allenynes driven by BCl3 was developed. This method provides a general and practical strategy to construct valuable pyrrolidines containing all-carbon quaternary centers or 3,5-dihydroazepine derivatives depending on the substituents of the allene, with conjugative and sterically hindered phenyl groups favoring the latter.
Enantioselective iodolactonization of allenoic acids
作者:Kenichi Murai、Nozomi Shimizu、Hiromichi Fujioka
DOI:10.1039/c4cc05414h
日期:——
An enantioselectiveiodolactonization reaction of allenoic acids has been developed using a trisimidazoline catalyst and I2. Our mechanistic study suggests the involvement of a pi-allyl cation intermediate in this reaction system.
made conveniently through condensation of corresponding isatins with N-diphenylmethyl amine, are deprotonated to form azaallyl anions. Allylation and alkylation of this type of intermediates proceed smoothly with diverse C-electrophiles. Acidic work up finishes 3-amino-3-allyl/alkyl oxindoles. The overall transformation equals to an umpolung process at the C3 of isatins.
Azasilines fused nitrogen heterocycles are prepared in excellent yields (from 74 to 98 % according to the structures) for the first time in one operation with high regio‐ and stereoselectivities. The key step consists of an intramolecular palladium‐catalyzed cyclisation reaction of heteroaryl disilane cores, bearing double or triple bond. We first studied the reactivity of pyridyl heterocycles, using xylenes
The first iron-catalysed cross coupling of propargyl electrophiles with lithium alkenylborates has been developed. Various propargyl electrophiles can be cross-coupled with lithium (E)- or (Z)-alkenylborates in a stereospecific manner to afford the corresponding 1,4-enynes in good to excellent yields. The reaction features high SN2-type regioselectivity and functional group compatibility.