From bromo esters

The addition of a-carbonyl radicals derived from bromo esters 47 to olefins 48 proceeded smoothly using 7.5-15 mol% of Ni(OAc)2 [100]. The reaction furnished reduced esters and amides 49 in 15-91% yield. Reactions to 1,2-disubstituted... 

Inanaga showed that the presence of HMPA also accelerates the Barbier addition of alkyl halides to ketones and significantly improves the yield of the adducts.14 He also found that HMPA was a useful additive in the Sml2-mediated synthesis of lactones from bromo esters and ketones (Scheme 2.5). Since Inanaga s pioneering work, the Barbier reaction employing Sml2 HMPA... 

Trost chose to exemplify the utility of organopalladium coupling reactions for carbon-carbon bond formation by use of this process for the ring closure step in a synthesis of 1 (Scheme 1.9) To this end, monoprotected diol 31 was oxidized and chain extended to form the a,p-unsaturated ester 32. Reduction to the allylic alcohol followed by acetylation and desilylation gave 33 in 53% overall yield from 31. Carboxylic acid 35 was then obtained via a two-step sequence from bromo ester 34 (84%) by alkylation with methyl... 

Addition of the Reformatsky reagent prepared from bromo ester 13 to imine 14 in benzene affords a 65% yield of trans jcis-fi-lactams 15 and 16 in 75 25 d.r. with trans-15 of d.r. [(3S,4R)/(3/f,4S)] 92 886. 

As mentioned in Sect. 2.3, Inanaga and co-workers have demonstrated that Barbier-type reactions of organic halides with carbonyl compounds are promoted by addition of HMPA [16]. They reported a mild convenient method for the direct synthesis of lactones from bromo esters and ketones or aldehydes by using a HMPA-promoted Barbier-type reaction with Sml2 (Scheme 13). They also found that the SmI2/THF-HMPA system was highly useful for the generation of... 

Aryl-/8-methylene-a-amino-acid esters [e.g. (165)] can be obtained from bromo-esters [e.g. (164)] by reaction with ammonia in DMSO the method fails in other solvents. ... 

Cyclization of carbanions derived from bromo-esters of type (18) has been exploited by Kondo et al in a useful approach to chrysanthemic analogues (Scheme 9), and the related base-induced cyclizations of yS-unsaturated epoxides and of epoxysulphones o to appropriate cyclopropanes have also received attention. 

This method with some slight modihcations is applied in the synthesis of to-bromo esters from Cs to Cn. Methyl 5-bromovalerate has been prepared by treating the silver salt of methyl hydrogen adipate with bromine. The ethyl ester has been prepared from the acid by esterification or through the acid chloride. ... 

The methyl ester (100, R = CH3), derived from this A-nor acid by treatment with diazomethane, is different from the ester (102) obtained either by Favorskii rearrangement of 2a-bromo-5a-cholestan-3-one (101) or by the action of cyanogen azide on 3-methoxy-5a-cholest-2-ene (103) followed by hydrolysis on alumina. The ketene intermediate involved in photolysis of (99) is expected to be hydrated from the less hindered a-side of the molecule to give the 2j -carboxylic acid. The reactions which afford (102) would be expected to afford the 2a-epimer. These configurational assignments are confirmed by deuteriochloroform-benzene solvent shifts in the NMR spectra of esters (100) and (102). ... 

We felt the Reformatsky reaction was a worthwhile target because it is the most generally applicable method for converting aldehydes and ketones to ff-hydroxyesters(25). The improvements in yield and reaction time exceeded our expectations. Essentially quantitative conversion to the 0-hydroxyester was effected in a matter of a few minutes(26). The absence of other products, such as a, 0-unsaturated esters, resulting from dehydration, and dimers of the bromo ester and the carbonyl are probably the result of running... 

Ethyl a-bromopropionate is available commercially (Sapon Laboratories, % 1.4452) and is employed without purification. Bromo esters are severe lachrymators, and operations that involve transferring these compounds from one vessel to another should be conducted in a well-ventilated hood. 

Ref 2), later from the 2-bromo ester and silver nitrate in acetonitrile (Ref 3) . by oxidizing 1-nirropopatrfe-l with nitric acid followed by esterification (Re/ 4), by reacting silver nitro-form with the 2-bromo ester (Ref 5) and by reacting the 2-bromo or iodoester with nitric acid (Ref 6)... 

Diazomethane yields the isomeric pyrazolines 40 and 41, respectively, from the bromo esters 38 and 39. These undergo an autocatalytic exothermic conversion to the same 1 //-pyrazole 42 on heating, or on standing in solution (Scheme 13). This is taken as evidence that 25 is an intermediate, because if group migration was concerted with loss of Br , 40 and 41 should give different products.89... 

Using an a-bromo ester instead of an a-bromo ketone the 2-hydroxyindolizine (111) has been obtained from ethyl 2-pyridylacetate (63JCS3277, 80JOC5100). By variation of R1 in (106), 1-cyano-, 1-amino-, 1-hydroxy- and 1-nitro-indolizines have been obtained. 

It was also reported that 7V-acyl-/V-hydroxyamino acids are readily synthesized from a-bromo esters 130 and dehydrated to form the dehydro compounds. A number of N-terminal Gly dipeptides having AAla, AAbu, ANva, and APhe at the C-terminus have been prepared in this manner. 131-133 ... 

This is a general method for preparing a-bromo acids. By using exactly analogous directions -bromo- -caproic acid may be obtained in 65-70 per cent yields from w-butylmalonic ester a-bromo-isocaproic acid in 65-70 per cent yields from isobutylmalonic ester and a-bromo-/3-methyl valeric acid in 75-80 per cent yields from sec.-butylmalonic ester. 

The 2//-l,3-oxazine ring was first described by King and Durst202 who revised earlier work of Kohler and Blatt203 and established that the anhydro compounds formed by the action of alkalis on isoxazolium salts are 2H-1,3-oxazines (66) [Eq. (52)]. The same ring system is obtained from an a-cyano-a-bromo ester with triisopropyl phosphite through an... 

Tellurium-Wittig reactions.1 The reaction of aldehydes with a-bromo esters or ketones, triphenyl phosphite, and a weak base in the presence of a catalytic amount of Bu2Te results in ct, l-unsaturated esters and ketones. The function of the triphenyl phosphite is the regeneration of Bu2Te from the dibutyl telluroxide formed in the... 

---