Ethyl o - Bromomethyl Acrylate

B Ethyl a (bromomethvl)acrylate In a nitrogen flushed, 1 L, round-bottomed flask equipped with a magnetic stirrer, Dean-Stark trap, and condenser are placed 42 0 g (0 25 mol) of a-(bromomethyl)acryhc acid and 300 mL of benzene Approximately 50 mL of a binary azeotrope of benzene and water is distilled (Note 7) The Dean-Stark trap is removed and 100 mL of absolute ethanol (Note 8) and 1 mL of concentrated sulfunc acid are added slowly The contents of the flask are boiled in a nitrogen atmosphere tor 36 hr, the condensate being passed through 100 g of molecular sieves Llnde 3A) before being returned (o the flask About 125 mL of a mixture of benzene and ethanol is removed from the reaction 

1 The checkers prepared this ester on a 0 7-mol scale by a modification of the previously published method The modification was effected as follows The ethereal extract from the formaldehyde-diethyl malonate reaction, after drying over sodium sulfate tor 3 hr, was concentrated in a rotary evaporator and the residue was stored in a refrigerator overnight The crude ester was obtained as white crystals mp 47-50°C, yield 85 6% The checkers found that the ester prepared in this manner gave superior yields of the acrylic acid 

2 The submitters reported that the use of excess hydrobromic acid resulted in the formation of a mixture of dibromoisobutyric acid and a (bromomethyl)acrylic acid as evidenced by NMR analysis 

4 This was done at 4°C to improve the yield, otherwise considerable amounts of a-(bromomethyl)acrylic acid remain in solution 

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Cahiez, Knochel, and co-workers have developed a mixed catalytic system consisting of MnBr2/GuGl and diethyl-zinc in iV,A -dimethylpropyleneurea (DMPU), which can be used for the stereocontrolled formation of tetrahydro-furan organozinc compounds from readily available unsaturated bromoacetals. The organozinc compounds are readily transmetalated with GuGN-2LiGl, and upon treatment with ethyl (o -bromomethyl)acrylate or ethyl propiolate homoallyl- and allyl-substituted bicyclic tetrahydrofurans are obtained in 71% and 63% yield (Scheme 70). 

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