2-Bromo-l-naphthols

An unusual domino process was observed by Biehl and coworkers [69] in the reaction of 2-bromo-l-naphthol 4-196 with arylacetonitriles in the presence of LDA or LiTMP by employing 3-thienylacetonitrile 4-197, the tetracyclic compound 4-200 was obtained in 57% yield (Scheme 4.43). The reaction probably includes the formation of an aryne and a ketenimine which undergo [2+2] cycloaddition to give 4-198, followed by rearrangement and allylic addition to the intermediately formed aryl cyano compound 4-199. 

In addition to the examples discussed above, arynes have also been found to insert into C-C single bonds. The reaction of either 2- or 3-bromophenol with arylacetonitriles in the presence of a strong base, such as lithium 2,2,6,6-tetramethylpiperidide (LiTMP), led to the same major products, 2-arylmethyl-6-hydroxybenzenecarbonitriles 23 (Scheme 12.9) [26]. In both cases, lithium 2,3-didehydrophenoxide (21) was generated. The anion of nitrile 20 then adds solely at the 3-position of 21 to afford adduct 22, which subsequently leads to the final product 23 after intramolecular rearrangement. When 2-bromo-l-naphthol was used instead of 2-bromophenol, a similar reachvity was observed [27]. 

Synthesis of DBA 3,4-dihydrodiol from DBA 3,4-dione via bro-mination and reduction of the 1,2-dibromo compound with sodium bo-rohydride has also been described (44). The DBA 3,4-dione was synthesized by Kundu from 5-bromo-2-nitro-l-naphthol in nine steps in 4.2% overall yield (45). More recently, reduction of DBA 3,4-dione with NaBH, in the presence of air has been reported to afford directly the 3,4-dihydrodiol (22). 

Chemical/Physical. An aqueous solution containing chlorine dioxide in the dark for 3.5 d oxidized naphthalene to chloronaphthalene, 1,4-dichloronaphthalene, and methyl esters of phthalic acid (Taymaz et ah, 1979). In the presence of bromide ions and a chlorinating agent (sodium hypochlorite), major products identified at various reaction times and pHs include 1-bromonaphthalene, dibromonaphthalene, and 2-bromo-l,4-naphthoquinone. Minor products identified include chloronaphthalene, dibromonaphthalene, bromochloronaphthalene, bromo-naphthol, dibromonaphthol, 2-bromonaphthoquinone, dichloronaphthalene, and chlorodibromo-naphthalene (Lin et ah, 1984). 

The use of this ester for the indirect conversion of an aryl halide to the corresponding phenol is illustrated by the preparation of 6-mcthoxy-2-naphthol (4) from 6-bromo-2-methoxynaphthalene (l).1 A mixture of the aryl halide (1), magnesium,... 

Bromo-2-naphthol is a source of 8-hydroxynaphtho[2,l-6]pyrans from which pyrano[3,2- ]naphtho[2,l-6]pyrans are formed on reaction with a 1,1-diarylprop-2-yn-l-ol. These molecules absorb at ca. 390 nm in the UV and at ca. 490 nm following irradiation <95USP5674432>. 

Nowadays, the trend appears to be to determine simultaneously iron and other metals or Fe(II) and Fe(III) species. In the first case, some reagents such as l,5-bis(di-2-pyridylmethylene)thiocarbonohydrazide, 2,4,6-tri-(2-pyridil)-l,3,5-triazine are used. In the second case 4,5-dihydroxy-l,3-benzenedisulfonic acid, disodium salt (635 nm), l-(5-bromo-2-pyridyla-zo)-2-naphthol-6-sulfonic acid (765 and 850 nm), azide complexes in tetrahydrofuran (396 nm), etc. are used... 

Thiolates can also cause dehalogenation of various halogen compounds, such as 2-bromo-3-nitro-thiophene and 2- and 4-halo-l-naphthols ... 

CL reaction can be catalyzed by enzymes other than HRP (e.g., microperoxidase and catalase) and by other substances [hemoglobin, cytochrome c, Fe(III), and other metal complexes]. The presence of suitable molecules such as phenols (p-iodophenol), naphthols (l-bromo-2-naphthol), or amines (p-anisidine) increases the light production deriving from the HRP-catalyzed oxidation of luminol and produces glow-type kinetics [6, 7], The use of other enzymes, such as glucose-6-phosphate dehydrogenase [38-41], P-galactosidase [42], and xanthine oxidase [43-46], as CL labels has been reported. 

Further bromination of 3,4,6-tribromo-5-hydroxybenzo[6]thio-phene affords the 2,3,4,6-tetrabromo derivative in the absence of acetate ion, and 3,4,4,6-tetrabromo-4,5-dihydrobenzo[6]thiophen-5-one in the presence of acetate ion. 421 On treatment of 3,4-dibromo-, 4,6-dibromo-, 3,4,6-tribromo-, or 2,3,4,6-tetrabromo-5-hydroxybenzo-[6]thiophene with nitric acid in acetic acid, the corresponding unstable orange crystalline 4-bromo-4-nitro-4,5-dihydrobenzo[6]thio-phen-5-one is obtained.152,421 Hence, once both positions ortho to the hydroxyl group in 5-hydroxybenzo[6]thiophene are occupied by bromine, the properties of these compounds are analogous to the properties of l-bromo-2-naphthol which, on bromination in acetic acid in the presence of acetate ion, affords l,l-dibromo-l,2-dihydro-naphthalen-2-one whereas, in its absence, it affords l,6-dibromo-2-naphthol.616 The behavior of l-bromo-2-naphthol and its derivatives on nitration is similar to that of 4,0-dibromo-5-hydroxybenzo[6]thio-phene and its derivatives.162,616... 

Methods for the histochemical localization of /3-glucuronidase, employing the /3-glucuronides of 1-naphthol, 6-bromo-2-naphthol, l-(2-hydroxy-phenylazo)-2-naphthol, and 8-quinolinol as substrates, have been critically examined by Burton and Pearse.146 The last-named substrate gave the least unsatisfactory results, and the technique compares not unfavorably with histochemical methods for other enzymes. 

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