Benzo 2-bromo-4-methoxy

Such reactions have also been carried out on benzofurans carrying benzyl, fluoro, chloro, bromo, methoxy, cyano, and phenyl groups in the benzo ring. Substitution in the stilbene part of the molecule can also be obtained by the use of Schiff s bases derived from differing benzal-dehydes.26,28,29... 

Tetrahydrobenzo[6]thiophene103 and several benzo[6]thio-phenes containing electron-donating substituents, e.g., 5,6-dimeth-oxy,180 5,6-methylenedioxy,180 6-ethoxy,424 3-methoxy,183 and 3-methyl,487 are smoothly brominated in the 2-position by iV-bromo-succinimide in carbon tetrachloride or chloroform in the absence of peroxides. Similar treatment of 2-methoxybenzo[6]thiophene gives the 3-bromo derivative.183... 

Tribromo-m-cresol is oxidized by chromium trioxide in 70% acetic acid at 70-75 °C within 10 min to dibromo-m-toluquinone (3,5-dibromo-2-methyl-p-benzophenone) in 77% yield [559]. 2-BVomo-4-hy-droxy-5-methoxybenzyl alcohol treated with Fremy salt at pH 6 at room temperature for 1 h gives an 84% yield of 2-bromo-5-methoxy -benzo-quinone [487]. 4-Benzyl-2,6-dibromophenol, on oxidation with bromine in a sealed tube, yields 2,6-dibromophenylchinomethide [732] (equation 312). The oxidation of 2,5-di-tert-butyl-4-methoxyphenol with mercuric oxide or... 

In contrast, 4,5-dimethyl-2-methoxy-l,3,2-dioxaphospholane reacts sluggishly with ethyl chloroacetate and only ethyl bromoacetate leads to the desired five-membered cyclic phosphonates as mixtures of the racemic and meso isomers. The 2-ethoxy-benzo[l,3,2]dioxaphosphole on reaction with chloro-, bromo-, or iodoacetate at 200-230°C leads to the 2-(ethoxycarbonyl)methyl-2-oxo-benzo[l,3,2]dioxaphosphole in variable yields (42-58%). ... 

The intramolecular trapping of benzyne intermediates with tethered nucleophiles is a powerful strategy for the synthesis of benzo-fused heterocycles. In this field, 7-functionalized benzoxazoles 59 and benzothiazoles 60 have been prepared by anionic cyclization of the corresponding lithiated benzyne (thio)amides and (thio)carbamates, which were generated from 3-haloaniline derivatives (Scheme 12.34) [55]. Related to this, substituted indolines 61 have also been accessed by benzyne-mediated cyclization-functionalization from Boc-protected (2-bromo-4-methoxy)phenetylamines using Mg(TMP)2 2LiCl as a base. This methodology has also been applied to the preparation of functionalized carbazoles (Scheme 12.34) [56]. 

Nucleophilic Substitution, Metallation, and Halogen-Metal Exchange.—Direct nucleophilic displacement of the 7-chloro-group of 7-chloro-3-methyl-benzo[b]thiophen has been achieved. 3-Bromobenzo[b]thiophen was reduced to the 3-deuterio-derivative by the reaction with sodium borodeuteride and palladium chloride. Meisenheimer complexes were formed in the reaction of methoxide ion with 2-methoxy-3-nitro- and 3-methoxy-2-nitrobenzo[b]thiophen. Rate and equilibrium data were determined in methanol at 25 C. On treatment of 2-bromobenzo[b]thiophen with potassium amide in liquid ammonia, bromine migration to the adjacent carbon atom was observed. Considerable evidence for the occurrence of an intermolecular transbromination was obtained. The reaction of 3-bromo-benzo[b]thiophen with piperidine has been reinvestigated and found to give primarily the normal, but also some of the cine-substitution product, which is the only product obtained in the reaction of 2-bromobenzo[b]thiophen. Possible mechanisms for some of these reacticms are suggested. 

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