Cyclopenten-1-ylboronic acid

Cyclopenten-1-ylboronic acid is prepared as follows:

The first step of the raw material 1-chlorocyclopentene preparation: to a 2L four-necked bottle equipped with magnetic stirring, thermometer, condenser tube and exhaust gas alkali absorption device, add 374.2 (1.818mol, 1.05) phosphorus pentachloride, 863g of n-heptane, warming to 70 , drop 151.4g (1.803mol, 1eq) cyclopentanone, about 2 hours after the drop, and continue the reaction Half an hour, after cooling down to 0 , dropwise addition of 6 mol / L sodium hydroxide solution 0.69 kg, stirring for one hour, separation of the upper organic layer, the organic layer was washed once with saturated sodium bicarbonate, to obtain 1-chlorocyclopentene n-hexane solution 799 g, the internal standard yield of 81.1%;

The second step of preparation of cyclopenten-1-ylboronic acid: to a 5L four-necked flask equipped with mechanical stirring, thermometer, argon protection and reflux condenser tube was added T2215.5g (1.608mol, 1.1eq), lithium metal 22.6g (3.216mol, 2.2eq), tetrahydrofuran 678g, cooled down to -10C, and dropwise addition of 1-chlorocyclopentene's Heptane solution (1eq), titration is completed insulation -10 stirring 11 hours, GC control, the end of the reaction, add 1.3kg6N hydrochloric acid adjust PH = 2 ~ 3, stratification, the aqueous layer and then 400g of ethyl acetate extracted once, combined with the organic layer, 40 distillation under reduced pressure, to not flow, precipitation of solids, add 200g of n-heptane-10 pulp, filtration, drying to obtain the white solid cyclopentene -1-ylboronic acid 89.3g, yield 54.5%.