Chromium-catalyzed cyclopropanation of alkenes with bromoform in the presence of 2,3,5,6-tetramethyl-1,4-bis(trimethylsilyl)-1,4-dihydropyrazine

Abstract

Chromium-catalyzed cyclopropanation of alkenes with bromoform was achieved to produce the corresponding bromocyclopropanes.

Nickel Nanoparticle Catalyzed Mono‐ and Di‐Reductions of gem‐Dibromocyclopropanes Under Mild, Aqueous Micellar Conditions

“…Note that mono‐reduction leading to 23 corresponds to the monobromide of API intermediate 13 . Recent literature provides an alternative, direct route to mono‐bromocyclopropanes from olefins using catalytic chromium, bypassing dihalocyclopropane intermediates . The method disclosed herein, however, avoids highly toxic metals and associated use of organic solvents, while yields of the mono‐brominated products prepared in water remain high throughout this 2‐step process.…”

“…propanes from olefins using catalytic chromium, bypassing dihalocyclopropane intermediates. [25] Them ethod disclosed herein, however,avoids highly toxic metals and associated use of organic solvents,w hile yields of the mono-brominated products prepared in water remain high throughout this 2step process.…”

An α‐Cyclopropanation of Carbonyl Derivatives by Oxidative Umpolung

“…The syntheses of cyclopropanes are often mediated by metals, but metal free approaches are also known such as the Johnson–Corey–Chaykovsky reaction . Several reviews have been published .…”

“…Although trans selectivity for the cyclopropanation was excellent and yields were typically higher, the reaction showed no selectivity over a third stereogenic center in the cyclopropylcarbinyl position (16 mb), possibly a result of the intermediacy of a highly stabilized tertiary cyclopropylcarbinyl cation. [61] The syntheses of cyclopropanes are often mediated by metals, [62][63][64] but metal free approaches are also known [65,66] such as the Johnson-Corey-Chaykovsky reaction. [67,68] Several reviews have been published.…”

Recent advances in metal-mediated nitrogen oxyanion reduction using reductively borylated and silylated N-heterocycles

“…Silyl substituted reduced N-heterocycles were first synthesized by Kaim, 33,34 and later pioneered by Mashima, 35 and are used for salt free reduction of transition metal complexes, [36][37][38] cyclopropanations, 39 and a variety of metal free deoxygenations of organic substrates. 40 Likewise, pioneered by Suginome, 41 the boryl substituted reduced N-heterocycles are employed in organocatalytic deoxygenations, 42 reductions of alkynes, 43 and de-aromatization of substituted pyrazines (Fig.…”