Generation and Reactions of o‐Bromophenyllithium Without Benzyne Formation Using a Microreactor.

Abstract

Halogen compounds Q 0090Generation and Reactions of o-Bromophenyllithium Without Benzyne Formation Using a Microreactor. -A new method is presented to study conversions with highly unstable intermediates. In situ generated o-bromophenyllithium is treated in a new microreactor system with various electrophiles at -78°C to avoid decomposition. In all cases, the corresponding ortho-substituted bromobenzene derivatives are formed. The procedure is also applicable to the sequential reaction with two electrophiles which is performed in a microsytem consisting of four micromixers and four microtubes. The first Br-Li exchange must also be performed at -78°C whereby, the second one can be performed at 0°C since the aryllithium intermediate is more stable than o-bromophenyllithium. -(USUTANI, H.; TOMIDA, Y.; NAGAKI, A.; OKAMOTO, H.; NOKAMI, T.; YOSHIDA*, J.-I.; J.

Anionic polymerization of alkyl methacrylates using flow microreactor systems

“…Recent investigations revealed significant features of flow microreactor systems involving fast mixing stemming from short diffusion path and fast heat transfer by virtue of high surface-tovolume ratio, which are advantageous to increase the selectivity of chemical reactions [17][18][19]. Short residence time in a microchannel is beneficial for controlling highly reactive intermediates [20][21][22][23][24][25][26][27]. By taking advantages of such features of flow microreactor systems, various chemical reactions for organic synthesis have been developed so far.…”

Micro-separation of fluid systems: A state-of-the-art review

“…Most of micro-chemical processes are limited either to a single reaction step or to multiple reaction steps without intermediate separation operations [106][107][108][109][110][111][112][113][114]. There are difficulties encountered when linking micro-unit operations together.…”

Synthesis of Organometallic Compounds in Flow

“…Monolithiation with BuLi of ortho ‐dibromobenzene ( o ‐DBB) is very challenging because it can easily eliminate LiBr generating benzyne. Yoshida showed that using a two‐stage microreactor technology, monolithiated o ‐bromobenzene could be prepared without this side reaction, allowing the functionalization with different electrophiles ( Figure ,a ) …”

“…Yoshida showed that using a two-stage microreactor technology, monolithiated o-bromobenzene could be prepared without this side reaction, allowing the functionalization with different electrophiles (Figure 1,a). [12] Residence time was optimized by varying the length of the tube R1 with a fixed flow rate. Best results were obtained when conducting the reaction at À 78°C with a residence time of 0.8 s. The use of elevated flow rates combined with a T-mixer, leads to a better mixing that might explain the selective formation of the unstable lithiated species.…”