Dibromoacetate

Dibromoacetic acid [631-64-1] (Br2CHCOOH), mol wt 217.8, C2H2Br202, mp 48°C, bp 232—234°C (decomposition), is soluble in water and ethyl alcohol. It is prepared by adding bromine to boiling acetic acid, or by oxidi2ing tribromoethene [598-16-3] with peracetic acid. 

Haloacetic acids dichloroacetic acid (zero) trichloroacetic acid (0.3 mg/L). Monochloroacetic acid, bromoacetic acid, and dibromoacetic acid are regulated with this group but have no MCLGs. 

The [6.5.5]-ring fused tricyclic motif is found in many natural products, and has therefore become an important target in synthesis. A convenient access to this structural framework is offered by a radical domino procedure published by the Nagano group [41]. This reaction of optical pure dibromoacetal 3-85 led to the desired tricycle 3-87 via 3-86 as a single diastereoisomer in a very respectable yield of 94% by applying classical radical conditions (excess tributyltin hydride/AIBN, irradia-... 

Ethyl dibromoacetate [105-36-2] M 245.9, b 81-82°/14.5mm, n22 1.4973. Washed briefly with cone aqueous NaHCC>3, then with aqueous CaCl2. Dried with CaS04 and distd under reduced pressure. 

CHBr2COOH (c). Pickering10 measured the heat of solution of dibromoacetic acid. 

Tritium in the acetyl moiety 175b has been obtained using, in a similar sequence of reactions, dibromoacetic acid and subsequent catalytic halogen-tritium exchange (equation 88). 

A reaction of dibromoacetic acid with different aldehydes promoted by Sml2, followed by an elimination reaction also promoted by samarium diiodide, affords ( > ,/l-unsaturalcd carboxylic acids with total stereoselectivity (Scheme 8).42 A mecha- (g) nism that involves chelation of the Sm(III) centre with the oxygen atom of the alcohol group through a six-membered chair-like transition state has been described. 

Stereoselective synthesis of (+ )-botryodiplodin was carried out by a radical cyclization of dibromoacetal (203) containing an allene group, with Bu3SnH initiated by Et3B, through the 5-exo-trig cyclization, and the subsequent debromination with bulky... 

Nesmeynov s and Freidlina s groups studied Kharasch additions of methyl dibromoacetate 31 to olefins 30 furnishing 2,4-dibromoesters 32 thoroughly in the 1960s and 1970s (Fig. 6) (review [89]). The preferred catalyst was iron... 

Freidlina et al. used 10 mol% of FeCl3 and 40 mol% of /V,/V-dimethylaniline to promote Kharasch additions of methyl dibromoacetate, methyl 2,2-dibromopropionate, methyl tribromoacetate, or dibromomalonate to acceptor-substituted olefins (cf. Fig. 6) [89]. Either linear addition products 32 or lactones were obtained in 23-60% and 43 -8% yield, respectively. 

More recently, Concellon has reported a stereoselective method for the formation of ( )-a,p-unsaturated esters that exploits a Sml2 Reformatsky reaction followed by an elimination.141 For example, ethyl dibromoacetate reacts with benzaldehyde in the presence of Sml2 to form samarium alkoxide 126, which is reduced further to give a second Sm(III) enolate 127. Elimination then affords ( )-a,p-unsaturated ester 128 in good yield (Scheme 5.90).141... 

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