Bromo acetals

This preparation illustrates the Reformatsky reaction, which consists in the interaction of a carbonyl compound, an a-halogen ester (e.g., ethyl bromo-acetate) and zinc In the presence of ether or benzene, followed by hydrolysis. 

The addition proceeds most smoothly with highly functionalized (more polar) steroids as seen in examples by Bernstein and others. The polar reaction conditions pose solubility problems for lipophilic androstane, cholestane and pregnane derivatives. Improved yields can be obtained in some cases by using dimethyl sulfoxide or t-butanol " as solvents and by using sodium A-bromobenzenesulfonamide or l,3-dibromo-5,5-dimethyl hydantoin (available from Arapahoe Chemicals) as a source of positive bromine. The addition of bromo acetate and bromo formate to steroid olefins has been studied to a limited extent. ... 

Hydrazinopyridazines such as hydralazine have a venerable history as anti hypertensive agents. It is of note that this biological activity is maintained in the face of major modifications in the heterocyclic nucleus. The key intermediate keto ester in principle can be obtained by alkylation of the anion of pi peri done 44 with ethyl bromo-acetate. The cyclic acylhydrazone formed on reaction with hydrazine (46) is then oxidized to give the aromatized compound 47. The hydroxyl group is then transformed to chloro by treatment with phosphorus oxychloride (48). Displacement of halogen with hydrazine leads to the formation of endralazine (49). ... 

Pentanal, 5-amino [14049-15-1], 121 Pentane, 1-bromo- [110-53-2], 82 Pentanediotc acid [ 110-94-1 ], 98 3-Pentenoicacid, 4-methyl- [504-85-8], 70 3-Penten-2-ol, 3-bromo-, acetate [14362-79-9], 35... 

Cupric oxide [Copper oxide (CuO)], 10 Cyclodecanone, 111 Cyclododecanone, 108 Cyclododecanone, 2,12-dibromo-, 107 1 -Cy cloheptene, 1 -bromo-7 -acety loxy-[2-Cyclohepten-l-ol, 2-bromo-, acetate], 34... 

Pentenoic acid 4-methyl-, 70 3 Penten 2-ol, 3 bromo, acetate, 35 3-Penten-2-ol, 3-bromo-4-methyl-, acetate,... 

Preparation of the quaternary anticholinergic agent benzilonium bromide (47) is begun by conjugate addition of ethylamine to methylacrylate, giving aminoester 42. Alkylation of 42 with methyl bromo-acetate leads to diester 43, which is transformed into pyrrolidone 44 by Dieckmann cyclization, followed by decarboxylation. Reduction of 44 by lithium aluminum hydride leads to the corresponding amino-alcohol (45). Transesterification of alcohol 45 with methyl benzilate leads to 46. Benzilonium bromide (47) is obtained by alkylation of ester 46 with ethyl bromide. 2... 

Reaction of p-fluorobenzyl chloride with the anion of diethylmethylmalonate ester followed by saponification and decarboxylation leads to acid 9. Polyphosphoric acid cyclization leads to indanone 10. A Reformatsky reaction with zinc amalgam and bromo-acetic ester leads to carbinol 11 which is then... 

A similar reaction of 1 with the bromo acetal S also proceeds with retention to provide 6, a useful precursor to unusual amino acids. 

Table 7. Alkylation of a-Enolates 2 of Chiral Iron -Acyl Complexes 1 by terf-Butyl Bromo-acetate (4)...

Bienayme and Yezeguelian [63] described a new synthesis of retinal via a Heck vinylation of a C15 tertiary allylic alcohol with a C5 iodoacetal. Thus, the bromo acetal was prepared by a known procedure [64], by a bromination-dehydrobromination reaction sequence (E and Z isomers 40/60). 

P-Bromo acetals and ketals. These useful derivatives are generally prepared by addition of an a./J-unsaturated carbonyl compound to a solution of HBr in the diol. The same products can be obtained by addition of HBr to the a,/J-enal or enone followed by acetalization. The method is improved if only a stoichiometric amount of HBr is used. Dicinnamalacetone (equation I)2 is used to determine the end point. Hydrogen bromide is added to the initially yellow solution until a red color persists. 

The reaction product of indomethacin (see below) with benzyl bromo acetate can also be hydrogenated to Acemetacin. 

However, the relative rates with His 12 and 119 vary widely depending on the structure of the reagent. The d antipodes generally favor reaction at His 12, the l compounds at His 119. No convincing correlation of all these facts with the X-ray structure has yet been made. In view of the fact that sulfate or phosphate ions seriously interfere with the alkylation reaction 160), the X-ray structures determined in the presence of these ions may be misleading. However, Bello and Nowoswiat have shown (69) that with RNase-A in crystalline form the alkylation with bromo-acetic acid is comparable, but not identical, to that found in dilute solution. 

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