Photolysis Of 2a Research Articles

Thermal and photochemical transformations of 1-(arylazo)-n-arylidene-2-naphthylamines

1-(Arylazo)-N-arylidene-2-naphthylamines 3a-e, prepared by the reaction of 1-(arylazo)-2-naphthylamines 1a,b with aromatic aldehydes 2a-d on refluxing in toluene, gave the corresponding 1-(arylamino)-2-phenylnaphth(1,2-d)imidazoles 6a-e in yields ranging between 50 and 60%. Refluxing of 3e in p-dichlorobenzene, however, gave 1H-2-phenylnaphth(1,2-d)imidazole (7, 45%) and 2H-2-phenylnaphtho(1,2-d)trazole (9, 5%). Reaction of 3a with dimethyl acetylenedicarboxylate gave dimethyl benzo(f)quinoxaline-2,3-dicarboxylate (10, 11%), dimethyl ..cap alpha..-benzal-..cap alpha..'-((1-(phenylazo)-2-naphthyl)imino)succinate (11, 7%), dimethyl (1-(phenylazo)-2-naphthyl)aminofumarate (12, 2%), and benzanilide (13, 6%). The reaction of 1-(phenylazo)-2-naphthylamine (1a) with dimethyl acetylenedicarboxylate (DMAD), however, gave 10 (32%) and 12 (3%). Photolysis of 3a in benzene gave 2H-2-phenylnaphtho(1,2-d)triazole (9, 5%) and N-benzoyl-1-(phenylazo)-2-naphthylamine (19, 41%), whereas the photolysis in methanol gave a mixture of 6a (10%), 19 (25%), 1a (1%), and the naphthotriazole 9 (4%). Reasonable mechanisms have been suggested for the formation of the various products in these ractions.

Synthetic and structural studies of [6]-, [7]- and [10]metacyclophanes

A new preparative sequence from 2,3-polymethylene-2-cyclopentenone 5 to 2,6-polymethylenebromobenzenes 3 (n = 6, 7, 10) and 2,6-polymethylenephenyllithiums 6 has been found. The reaction of 6 with various electrophiles produces a number of new compounds to disclose the unique reactivity of the aryl C-Li moiety surrounded by the polymethylene chain. Photolysis of 3a and 3b provides transannular products 8, 10 and 11, all arising from the proximity between the aromatic bromine and the aliphatic hydrogen intraannularly opposed to be removed as HBr. Spectrometric study gives quantitative data of the dependence of the molecular geometry upon the chain length and the aromatic substituents. The energy barriers ΔG c ≠ of the conformational flipping are 17·4 kcal/mol (T c 76·5°) for [6]metacyclophane ( 7a), 11·5 kcal/mol (T c −28°) for [7]metacyclophane ( 7b), ·8 kcal/mol for [10]metacyclophane ( 7c). The lower-energy process of the aliphatic chain in [6]metacyclophane derivatives is the pseudorotation with substituent-dependent barrier ΔG c ≠ 11·1 kcal/mol (T c −31·5°) for 7a, 12·4 kcal/mol (T c −4·5°) for 3a and 12·7 kcal/mol (T c 1·0°) for 12a. The rather large rotational barrier is attributed to the compressed structure of each system. The benzene ring distortion of the cyclophanes is deduced from the bathochromic shift of the B-band and the diamagnetic shift of the benzene proton signals in the PMR.