3- Nitrobenzyl bromide

Dicbloronitrobenzene o-Nitrobenzyl chloride m-Nitrobenzyl chloride p-Nitrobenzyl chloride o-Nitrobenzyl bromide m-Nitrobenzyl bromide p-Nitrobenzyl bromide o-Nitrobenzyl iodide m-Nitrobenzyl iodide p-Nitrobenzyl iodide o-Nitrobenzyl cyanide... 

Care must be taken in manipulating the lachrymatory solutions of p-nitrobenzyl bromide. If the substance should come into contact with the skin, bnthe the affected part with alcohol. 

Hydroxy-5-nitrobenzyl bromide [772-33-8] M 232.0, m 147", pK st -8.0. Crystd from benzene or benzene/ligroin. 

Nitrobenzyl bromide [100-11-8] M 216.0, m 98.5-99.0 . Recrystd four times from abs EtOH, then twice from cyclohexane/hexane/ benzene (1 1 1), followed by vac sublimation at 0.1mm and a final recrystn from the same solvent mixture. [Lichtin and Rao J Am Chem Soc 83 2417 1961.] Has also been crystd from pet ether (b 80-100°, lOmL/g, charcoal). It slowly decomposes even when stored in a desiccator in the dark. IRRITANT. 

A mechanism of this type permits substitution of certain aromatic and ahphatic nitro compounds by a variety of nucleophiles. These reactions were discovered as the result of efforts to explain the mechanistic basis for high-yield carbon alkylation of the 2-nitropropane anion by p-nitrobenzyl chloride. p-Nitrobenzyl bromide and iodide and benzyl halides that do not contain a nitro substituent give mainly the unstable oxygen alkylation product with this ambident anion ... 

We first tried to prepare 1-hydroxyyohimbine (23) and its derivatives. With 23 in hand (as described in Section II.D), its methylation with CH2N2 is carried out to provide 1-methoxy derivative 304 (77%) (Scheme 47). Utilizing K2CO3 as a base in DMF, allyl bromide, butyl iodide, and p-nitrobenzyl bromide react successfully with 23, resulting in the formation of 305 (93%), 306 (99%), and 307 (90%), respectively. All of these compounds, including 23 itself, are found to exhibit potent Q 2-blocking activity (2001H1237), and the details will be reported in due course. 

Reslurrying can sometimes be advantageously employed for removal of impurities adsorbed on the surface. Anderson (2000) has given an example of the removal of excess p-nitrobenzyl bromide from a modified penicillin by reslurrying. 

Previous syntheses An example of this point can be recognized by examination of one known synthesis of thienobenzazepines (Scheme 6.1). This synthetic route involves a key palladinm-catalyzed cross-conpling of stannyl intermediate 3, prepared by method of Gronowitz et al., with 2-nitrobenzyl bromide. Acetal deprotection and reductive cyclization afforded the desired thienobenzazepine tricycle 4. In support of structure activity relationship studies, this intermediate was conveniently acylated with varions acyl chlorides to yield several biologically active componnds of structure type 5. While this synthetic approach does access intermediate 4 in relatively few synthetic transformations for stractnre activity relationship studies, this route is seemingly nnattractive for preparative scale requiring stoichiometric amounts of potentially toxic metals that are generally difficult to remove and present costly purification problems at the end of the synthesis. 

Horton, H. R. Koshland, D. E. Jr. A highly reactive coloured reagent with selectivity for the tryptophan residue in proteins 2-hydroxy-5-nitrobenzyl bromide. J. Amer. Chem. Soc. 1965, 87, 1126-1132. 

The drug discovery route to rizatriptan (1) began with the preparation of 1-(4 -nitrobenzyl)-l,2,4-triazole 5 using 4-nitrobenzyl bromide (4) and 1,2,4-triazole. (Scheme 4.1). Benzylation of the sodium salt of 1,2,4-triazole prepared with NaH was not regioselective and afforded a 1.5 1 mixture of l-(4 -nitrobenzyl)-1,2,4-triazole (5) and its regioisomer, 4-(4 -nitrobenzyl)-l,2,4-triazole. The desired isomer 5 was isolated in 52% yield after silica gel chromatography. Hydrogenation... 

Process development of the synthesis of iodoaniline 28 began with an improved synthesis of l-(4 -aminobenzyl)-l,2,4-triazole (6) (Scheme 4.7), which was prepared in the medicinal chemistry synthesis, albeit with poor regioselectivity (Scheme 4.1). We found that this aniline intermediate 6 could be readily prepared in three steps in >90% overall yield from 4-amino-l,2,4-triazole (30) and 4-nitrobenzyl bromide (4) based on a modified literature procedure [9]. The condensation of 30 and 4 in isopropyl alcohol followed by deamination gave the nitro... 

A molecular dissection of the alkaloid vasicine (52) ultimately resulted in the expectorant and mucolytic agent bromhexine (54). The synthesis starts with displacement of halogen on 2-nitrobenzyl-bromide (53) by N-methyl cyclohexylamine, followed by Raney nickel and hydrazine reduction of the nitro group. Bromination in acetic acid then affords bromhexine. 

Following an explosion dining drying of 2-nitrobenzyl bromide, the thermal stability of all six isomeric nitrobenzyl halides was investigated by TGA, DSC and ARC techniques. All the halides decomposed exothermally with abundant gas evolution, and the 2-nitro chloride is less thermally stable than the 3- or 4-isomers. See 2-Nitrobenzyl bromide... 

A similar approach via desulfurization of the thiosemicarbazide-substituted pyrimidone 290 using 4-nitrobenzyl bromide leads to efficient formation of the tricyclic system 291 in excellent yield (Equation 79) <2000RJ0430>. 

Bromoadamantane and 1-bromoadamantane are reduced to adamantane in yields of 84% and 79%, respectively, when treated with triethylsilane and catalytic amounts of aluminum chloride.186 Similar treatment of benzhydryl chloride and exo-2-bromonorbomane gives the related hydrocarbons in yields of 100% and 96%, respectively.186 In contrast, 2-bromo-l-phenylpropane gives only a 43% yield of 1-phenylpropane the remainder consists of Friedel-Crafts alkylation products.186 Some alkyl halides resist reduction by this method, even when forcing conditions are employed. These include p-nitrobenzyl bromide, 3-bromopropanenitrile, and 5-bromopentanenitrile.186... 

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