Reported is the electrophilic amination of functional organolithium intermediates with well-designed aminating reagents under mild reaction conditions using flow microreactors. The aminating reagents were optimized to achieve efficient C-N bond formation without using any catalyst. The electrophilic amination reactions of functionalized aryllithiums were successfully conducted under mild reaction conditions, within 1 minute, by using flow microreactors. The aminating reagent was also prepared by the flow method. Based on stopped-flow NMR analysis, the reaction time for the preparation of the aminating reagent was quickly optimized without the necessity of work-up. Integrated one-flow synthesis consisting of the generation of an aryllithium, the preparation of an aminating reagent, and their combined reaction was successfully achieved to give the desired amine within 5 minutes of total reaction time.
In a flow microreactor, aryllithiums bearing a piperidylmethyl group were generated using nBuLi by precise residence time control and effective temperature control, and then selectively borylated with boronic esters such as 2-isopropoxy-4,4,5,5-tetramethyl-1,3,2-dioxaborolane (BpinOiPr) and trimethyl borate B(OMe) 3 by fast mixing. Moreover, the direct inte-Biaryl compounds bearing aminomethyl groups, such as piperidyl methyl, have attracted much attention because they are potential bioactive reagents (Figure 1). [1] Figure 1. The nitrogen-containing biaryl compounds.[a]
A chemoselectivity switchable microflow reaction was developed to generate reactive and unstable intermediates. The switchable chemoselectivity of this reaction enables a selection for one of two different intermediates, an aryllithium or a benzyl lithium, at will from the same starting material. Starting from bromo-substituted styrenes, the aryllithium intermediates were converted to the substituted styrenes, whereas the benzyl lithium intermediates were engaged in an anionic polymerization. These chemoselectivity-switchable reactions can be integrated to produce polymers that cannot be formed during typical polymerization reactions.
The rapid cis–trans isomerization
of α-anionic stilbene was regioselectively controlled by using
flow microreactors, and its reaction with various electrophiles was
conducted. The reaction time was precisely controlled within milliseconds
to seconds at −50 °C to selectively give the cis- or trans-isomer in high yields. This synthetic
method in flow was well-applied to synthesize precursors of commercial
drug compound, (E)- and (Z)-tamoxifen
with high regioselectivity and productivity.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.