Olga Rubio

The chemistry of N-substituted benzotriazoles. Part 1.1-(Chloromethyl)benzotriazole

The N-chloromethyl group of 1-(chloromethyl)benzotriazole undergoes nucleophilic substitution by carbon, nitrogen, phosphorus, oxygen, and sulphur nucleophiles. α-Lithiation was achieved in high yield in 1-phenylthiomethyl-, 1-phenylsulphinylmethyl-, and 1-(phenylstilphonylmethyl)benzotriazoles and the lithio derivatives reacted with a variety of electrophiles. New benzotriazolium salts were prepared by quaternization of the N-3 nitrogen with methyl iodide.

Reactions of pyridinium ylides with aldehydes and with Michael acceptors

1-Methyl and 1-allyl-2,4,6-triphenylpyridinium cations react with aromatic aldehydes at the α-CH2 to give aldol products (7) and (8). The allyl adducts (8) were thermally converted into aldehydes and ketones, whereas thermolysis of (7) took a variety of courses. Zwitterions from 1-methylpyridinium cations were also added Michael-fashion to activated carbon–carbon double bonds.

X-ray crystallographic structures of 9-methyl-3-oxa-2,6,8-triphenyl-5-azatri-cyclo[4,2,1,02,6]non-7-ene 6-hydroxy-1,6,7-triphenylazabicyclo[3,3,0]octa-2, 7-diene and 6-hydroxy-4-methyl-1,6,7-triphenylazabicyclo[3,3,0]oct-7-ene: products formed by rearrangements of N-vinylpyridinium pseudobases

Les composes cristallisent respectivement dans les systemes monoclinique, triclinique et orthorhombique

Some novel reactions of pyridinium-2-carboxylate betaines

Appropriate 2-ethoxycarbonylpyridinium salts are hydrolysed to 1 -aryl-4,6-diphenylpyridinium-2-carboxylate betaines which undergo thermal decarboxylation to afford, in the presence acids, 1 -aryl-2,4-diphenylpyridinium salts. The intermediate ylides are captured by acid chlorides to yield 2-acylpyridinium salts and by CS2, to give dithio analogues of the starting betaines. With bromine, the carboxylate betaine yields a 2,2′-bipyridyl bisquaternary salt.1-Benzyl-4,6-diphenylpyridinium-2-carboxylate with benzoyl chloride yields 2-benzoyl-4,6-diphenyrlpyridine and benzyl chloride. Benzaldehydes in place of PhCOCl, also gave 2-acylpyridines.

Nucleophilic displacements of N-aryl and heteroaryl groups. Part 6. The rearrangement of 1-aryl-5,6,7,8-tetrahydro-8-oximino-2,6-diphenylquinolinium cations

1 -Aryl-2-(benzyl- and neopentyl-carbamoyl) pyridinium salts (7) are rearranged by NaH at 110 °C into the corresponding 2-(N-aryl-N-substituted carbamoyl) pyridines (19). The 1 -aryl-5,6,7,8-tetrahydro-8-oximinoquinolinium salts (14) similarly give 8-(arylhydroxyamino)-5,6-dihydroquinolines (17), preferring a five- to a six-membered transition state.

The synthesis and chemistry of azolenines. Part 3. Some reactions of 4H-pyrazole quaternary salts

The preparation of some novel 4H-pyrazolium salts is described. Unlike the structurally related 2H-imidazolium salts (1), the metho-salts (2) of 4H-pyrazoles show no exchange with deuterium at the N-methyl protons. Exchange occurs readily at a 5-methyl group, anions formed at this site giving a cyanine dye (10) with triethoxymethane and benzylidene derivatives (11) and (12) with 1 mol equiv. of aromatic aldehyde. The activated benzylidene derivatives react further with an excess of aldehyde and base, apparently via an N-ylide intermediate, to give pyrazolo[5,1-b]oxazoles (15), which ring-open in the presence of acid forming N-(2-hydroxyethyl)-4H-pyrazolium salts (13). With sodium borohydride, the metho-salts (2) are reduced to 4,5-dihydropyrazoles (16), which with methyl iodide are quaternised at N-1 rather than N-2.