8-bromo-2,2 -dimethyl-6-nitro

Exposure of the 8-bromo-2,2 -dimethyl-6-nitro-l -phenyl-(2H-[l]benzospiro-pyran-2,2 -indoline) to light causes it to isomerize into the coloured form. In a solvent it rapidly converts to the bleached form and exhibits first-order kinetics.The process is thermally activated and will require volume for the relative rotation of the two parts of the molecule to effect ring closure. However, if the same process is carried out with the dye in a polymer matrix the process now depends on there free volume available for the rotation of the molecule required for ring closure to occur. Studies of the kinetics (Figure 7.15) indicate that simple kinetics is no longer followed and that a more complex analysis is required. Good fits of the data can be obtained if it is assumed that the process is split into two processes. The initial fast decay is essentially the same as that seen in a liquid and indicates that the ring closure process is only subject to thermal control. This implies that these molecules have sufficient free volume available to execute the process. 

Compounds 4 and 5 would be expected to be inert toward electrophilic substitution, and, in fact, sulfonation of the 2-phenyl derivative 201234 and nitration of the 1-phenyl derivative 202l69b lead to substitution on the phenyl rings. A series of electrophilic substitutions on the product (203) from 1 -(n-butyl)[l,2,3]triazolo[4,5-c]pyridine and dimethyl sulphate give 7-bromo-, 7-nitro-, and 7-chlorotriazolopyridin-4-ones the electrophilic attack may, in each case, be on the triazolopyridinone.169... 

When large groups, such as phenyl, bromo, ethoxycarbonyl or nitro are attached at position 3, the principal products are l-alkylcinnolin-4(l/f)-ones. Cyanoethylation and acetylation of cinnolin-4(l/f)-one takes place exclusively at N-1. Phthalazin-l(2/f)-ones give 2-substituted derivatives on alkylation and acylation. Alkylation of 4-hydroxyphthala2in-l(2/f)-one with an equimolar amount of primary halide in the presence of a base leads to 2-alkyl-4-hydroxyphthalazin-l(2/f)-one and further alkylation results in the formation of 4-alkoxy-2-alkylphthalazinone. Methylation of 4-hydroxy-2-methyl-phthalazinone with dimethyl sulfate in aqueous alkali gives a mixture of 4-methoxy-2-methylphthalazin-l(2/f)-one and 2,3-dimethylphthalazine-l,4(2//,3//)-dione, whereas methylation of 4-methoxyphthalazin-l(2/f)-one under similar conditions affords only 4-methoxy-2-methylphthalazinone. 

Pyrimidine, 5-benzyl-4,6-dimethyl-2-phenyl-synthesis, 3, 118 Pyrimidine, 2-benzyl-5-nitro-synthesis, 3, 130 Pyrimidine, benzyloxy-pyrimidinone synthesis from, 3, 133 Pyrimidine, 4,5-bis(alkylamino)-synthesis, 3, 121 Pyrimidine, 2-bromo-aminolysis, 3, 100 H NMR, 3, 62 reactions... 

Figure 5-4. 2-Bromo-2-bromomethylglutaronitrile, 2,2-dibromo-3-nitrilo-propionamide, 1,2-dimethyl-5-nitro-1 H-imidazole, 4,4-dimethyl-2-oxazo-lidinone, dimethylaminopropyl acrylamide, dimethylaminopropyl methacrylamide, or dimethylaminopropyl acrylamide, 5,5-dimethylhydantoin, dimethylurea.

Bromo-2,3-dimethoxy quinoxaline 6-Bromo-5,8-dimethoxy quinoxaline 6-Bromo-7,8-dimethyl-5-nitro-... 

Many of the reactions of A-chloro- and A-bromo-imides are extremely violent or explosive. Those observed include A-chlorosuccinimide with aliphatic alcohols or benzylamine or hydrazine hydrate A-bromosuccimmidc with aniline, diallyl sulfide, or hydrazine hydrate or 3-nitro-A-bromophthalimide with tetrahydrofur-furyl alcohol l,3-dichloro-5,5-dimethyl-2,4-imidazolidindione with xylene (violent explosion). Individually indexed compounds are ... 

Silane, (3, 5-dimethyl-2, 4, 6-trinitrophenyl) trimethyl-Benzene, 1, 3-Bis (1, l-dimethylethyl)-2-methoxy-5-nitro Benzene, 1-(1, l-dimethylethyl)-2-methoxy-3-nitro Benzene, 2-methoxy-4-methyl-l, 3,5-trinitro Benzaldehyde, 3-(l,l-dimethylethyl)-2-methoxy-5-nitro Benzene, 2-bromo-4- (l,l-dimethylethyl)-l,3, 5-trinitro Benzene, l-(l,l-dimethylethyl)-2, 4-dimethoxy-5, 6-dimethyl-... 

Several of the methods of synthesis of 2,2 -bipyridines have their counterpart in the preparation of 4,4 -bipyridine. The Ullmann reaction has been used to prepare 4,4 -bipyridine. Thus 4-halogenated pyridines afford 4,4 -bipyridine. Dehalogenation and dimerization of 4-bromopyridine may be accomplished too with hydrazine and alkali at 65°C in the presence of a palladium catalyst, whereas 4-chloropyridine is converted to 4,4 -bipyridine in 46% yield by reaction with alkaline sodium formate in the presence of palladium on charcoal and a surfactant. Several extensions of the Ullmann reaction have recently been reported, especially for the synthesis of substituted 4,4 -bipyridines. Thus 4-iodo-2-methylpyridine gives 2,2 -dimethyl-4,4 -bipyridine, 3-nitro-4-chloropyridine affords 3,3 -dinitro-4,4 -bipyridine, 4-bromo- or 4-iodotetrafluoropyridine gives octafluoro-4,4 -bipyridine, and 4-iodo- or 4-bromotetrachloropyridine gives octachloro-4,4 -bipyridine. Related syntheses have been de-... 

Chloro, 3-bromo, 3-iodo, and 3-nitro derivatives of 5,7-dimethyl-pyrazolo[l,5-a]pyrimidine derivatives were prepared by chlorination, bromination, iodination, and nitration of 3-unsubstituted 5,7-dimethyl-pyrazolo[l,5-a]pyrimidines. Reaction with bromine and potassium thiocyanate gave a 3-thiocyanato derivative, which was converted into the mercapto derivative upon saponification. Nitrosation gives the 3-nitroso derivative and acylation with trifluoroacetic anhydride affords the trifluoroacetyl derivative (74JMC645 77JMC386). 

Groups of reportedly photochromic systems which deserve further study include (a) disulfoxides (123,124), (b) hydrazones (125-129), (c) osazones (130-133), (d ) semicarbazones (134-143), (e) stilbene derivatives (144), (/) succinic anhydrides (145-148), and (g) various dyes (149,150). A number of individual compounds also remain unclassified as to their mechanism of photochromic activity. These include o-nitro-benzylidine isonicotinic acid hydrazide (151), 2,3-epoxy-2-ethyl-3-phenyl-1-indanone (152), p-diethyl- and p-dimethyl-aminophenyli-minocamphor (153), brucine salts of bromo- and chloro-nitromethionic acid (154), diphenacyldiphenylmethane (155,156), 2,4,4,6-tetraphenyl-1,4,-dihydropyridine (155,156), 2,4,4,6-3,5-dibenzoyltetrahydropyran (155,156), o-nitrobenzylidenedesoxybenzoin (157), p-nitrobenzylidene-desoxybenzoin (157), N-(3-pyridyl)sydnone (158,159), tetrabenzoyl-ethylene (160), and the oxidation product of 2,4,5-triphenylimidazole (161,162). 

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