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Generation of Diazomethyl Radicals by Hydrogen Atom Abstraction and Their Cycloaddition with Alkenes
Author(s) -
Su YongLiang,
Dong Kuiyong,
Zheng Haifeng,
Doyle Michael P.
Publication year - 2021
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.202105472
Subject(s) - diazo , chemistry , reactivity (psychology) , radical , cycloaddition , umpolung , regioselectivity , electrophile , intramolecular force , medicinal chemistry , hydrogen atom abstraction , hydrogen atom , photochemistry , catalysis , organic chemistry , nucleophile , alkyl , medicine , alternative medicine , pathology
A general catalytic methodology for the synthesis of pyrazolines from α‐diazo compounds and conjugated alkenes is reported. The direct hydrogen atom transfer (HAT) process of α‐diazo compounds promoted by the tert ‐butylperoxy radical generates electrophilic diazomethyl radicals, thereby reversing the reactivity of the carbon atom attached with the diazo group. The regiocontrolled addition of diazomethyl radicals to carbon‐carbon double bonds followed by intramolecular ring closure on the terminal diazo nitrogen and tautomerization affords a diverse set of pyrazolines in good yields with excellent regioselectivity. This strategy overcomes the limitations of electron‐deficient alkenes in traditional dipolar [3+2]‐cycloaddition of α‐diazo compounds with alkenes. Furthermore, the straightforward formation of the diazomethyl radicals provides umpolung reactivity, thus opening new opportunities for the versatile transformations of diazo compounds.