Bromine-lithium exchange on gem-dibromoalkenes part 1: batch vs microflow conditions

Abstract

The generation and reactivity of two model vinyl carbenoids from gem-dibromoalkenes 1 were studied in microflow systems. From substrate 1a (R = Ph, CF 3 ), the lithium-bromine exchange could be simply performed within 30 ms at 20 °C with very good E-selectivity whereas the reaction was unselective under batch conditions, even at 78 °C. Moreover, the unstable carbenoid generated from 1b (R = Ph, H) could be trapped as the major product while only the Fritsch-Buttemberg-Wiechell rearrangement product was obtained in a flask under cryogenic conditions.

A modular, low footprint and scalable flow platform for the expedient α-aminohydroxylation of enolizable ketones

“…The improved heat exchange efficiency under continuous flow conditions is typically exploited to perform highly exothermic reactions at higher temperatures than batch would normally allow. 108,109 Upon optimization, the enolization of ketone 2a in module I required 1 min of residence at 0°C with 1.1 equiv. of LiHMDS in THF (0.5 M), rather than typically −78°C in batch.…”

Flow neutralisation of sulfur-containing chemical warfare agents with Oxone: packed bed vs. aqueous solution

“…In this context, the use of miniaturised reactors operated in continuous flow have been shown to be invaluable tools to reach high selectivity sometimes unavailable under classical batch conditions. [13][14][15][16][17][18][19][20] Moreover, such devices offer the possibility to handle and treat large volumes of toxic and corrosive compounds without exposing the operator.…”

“…Due to superior mass transfer and fine residence time control obtained in flow microreactors consecutive competitive reactions can sometimes be avoided with significant enhancement in selectivity. [13][14][15]23,24,[33][34][35][36][37][38][39][40] Thus, we implemented a flow system where a methanolic solution of CEES was introduced at the first inlet and an aqueous solution of Oxone (C = 0.59 mol.L -1 ) at the second inlet, the reactor outlet being quenched with a solution of NaHSO 3 (Fig. 3, Method A).…”

Bromine–Lithium Exchange on a gem-Dibromoalkene, Part 2: Comparative Performance of Flow Micromixers

“…the shape of eight micromixers of circular cross-section from Y to W structure (angles  = 135, FBW) along with various side-reactions [10][11][12]. In a recent preliminary study, we showed that gem-dibromoalkene 1 was able to undergo lithium-bromine exchange and that the corresponding carbenoid intermediate A was stable enough to trap a proton to generate the…”