An efficient stereoselective synthesis of difluoromethylated alkenes in a microreactor

The synthesis of fluorinated materials in microreactors

“…These results prompted us to employ these materials as a Michael acceptor for the synthesis of difluoromethylated materials using the microreactor. As expected, Michael addition reactions of these materials with nitroalkanes in the presence of 1,8-diazabicyclo [5,4,0]-7-undecene (DBU) proceeded smoothly to afford the corresponding 1,4-adducts in the microreactors (channel width 100 mm, depth ca. 40 mm and length 120 mm; flow rate 1 ml min À1 ) without any detectable formation of polymeric products (Scheme 4).…”

“…In particular, compound 5 (entries 1 and 2: Ph (26%), 4-MeOC 6 H 4 (45%)) via the silylenol ether 3 was obtained as a minor material in the reaction at room temperature, however, compound 5 was not produced at À78 8C and in microreactor. In the previous reports, we have revealed the utilities of microreactor, such as the benefit of temperature control [4,5]. To avoid the formation of silylenol ether 3, we designed the microreactor shown in Fig.…”

“…In the above procedure, the mixture of nitromethane (1.2 M in THF) and (E)-ethyl 4,4-difluorocrotonate (1.2 M in THF) were injected via a syringe and syringe-pump, while 1,8-diazabicyclo- [5,4,, was also introduced via another syringe controlled with the same syringe-pump. The reaction was carried out in the microreactor (channel width 100 mm, depth ca.…”

“…All these properties make these systems excellent candidates for application in developing environmentally benign chemical process, and actually microreactors are widely diffused as greener alternatives to classical reactors in chemical transformation [3]. Recent investigations in this field have opened up the possibility for stereocontrolled synthesis of fluorinated materials at room temperature [4], along with the construction of fluorinated materials [2,5].…”

Flow microreactor synthesis in organo-fluorine chemistry

“…Kitazume et al demonstrated the benefit of flow microreactors for a highly stereoselective synthesis of difluoromethylated alkenes [ 51 ]. They succeeded in perfect control of rapid base-catalyzed isomerization to give ( E )-ethyl 3-difluoromethylpropenates ( Scheme 4 ).…”