Thermal rearrangement and fragmentation of 1a, 7b-dihydro-1H-cyclopropa[c]cinnolines

Heating of 1a, b in boiling xylene resulted in the rearranged products 2a, b , probably through concerted ring cleavage and 1,5-hydrogen shift. Under the same conditions, 1c reacted slowly to give a mixture from which the fragmentation products 4 and 5 were obtained.     

Approaches to 1H-Cyclopropa[l]phenanthrenes. Eliminations with 1a,9b-Dihydro-1H-cyclopropa[l]phenanthrene Derivatives

Base-induced elimination of the sulfonium salt 2i in the presence of furan affords the addition products 7 and 8 , derived from 1H-cyclopropa[l]phenanthrene ( 1 ) and the isomeric cyclopropene 5a (Scheme 3). Upon oxidation, the selenide 2c yields phenanthrene-9-methanol ( 9 ), presumably via 1 . No evidence for the intermediate 1 is obtained from sulfoxide pyrolysis with 2e , which leads to products formed by radical pathways (Scheme 5). Reductive elimination of the disulfone 3b gives half-reduction to monosulfone 2g and complete reduction to cyclopropane 2 as well as 9-methylphenanthrene ( 15 ), but no evidence for the intermediate 1 .     

General synthesis of 1a,7b-dihydro-1H-cyclopropa[c]cinnolines with electron-withdrawing substituents in the 1a-position

2-Vinylphenylhydrazonyl chlorides ( 4 ) react with triethylamine in boiling benzene to afford the title compounds ( 6 ) in 54–72% yield, probably through nitrile imine intermediates ( 5 ).     

[1,1-bis (trimethylsilyl)]-1H-cyclopropa [b] napththalene[tricarbonyl-chromium]: The first arene-chromium complex of a cycloproparene

[1,1-Bis (trimethylsilyl)]-1 H -cyclopropa [b] naphthalene rricarbonylchromium ( 2 ) was synthesized by reaction of 1,1-bis (trimethylsilyl) cyclopropa [b] naphthalene ( 1b ) with tricarbonyltris(acetonitrile) chromium.     

Ring transformation of 6H-cyclopropa[e]pyrazolo[1,5-a]pyrimidine. IV (1). Reduction and reaction of 5a-acetyl-6a-ethoxycarbonyl-5a,6a-dihydro-6H-cyclopropa[e]pyrazolo[1,5-a]pyrimidine-3-carbonitriles with primary amines

The reaction of 5a-acetyl-6-ethoxycarbonyl-5a,6a-dihydro-6H-cyclopropa[e]pyrazolo[1,5-a]pyrimidine-3-carbonitrile ( 1a ) with benzylamine gave ethyl l-benzyl-5-cyano-8a,9-dihydro-2-methyl-1H-pyrrolo[3,4-e]-pyrazolo[1,5-a]pyrimidine-8a-carboxylate ( 2a ), in addition to 5-acetyl-3-benzylamino-1-(4-cyanopyrazol-3-yl)- 2-pyridone ( 3 ). Reaction of 1a with aniline gave ethyl 6-acetyl-8-anilino-3-cyano-7,8-dihydro-4H-pyrazolo-[1,5-a][1,3]diazepine-8-carboxylate ( 4 ), in addition to ethyl 3-cyano-7-methyl-6-pyrazolo[1,5-a]pyrimidine-acrylate ( 5 ). On the other hand, the same reactions of 1b with benzylamine or aniline gave 2b or 8b , respectively. Though catalytic hydrogenation of 1a over 5% palladium-carbon proceeded by ring fission of cyclopropane ring to give 9 , 1a (or 1b ) afforded 4,5-dihydro derivatives ( 13 or 15 ) by catalytic hydrogenation over platinum oxide. The reactivity of 5-methoxy-4,5,5a,6a-tetrahydro-6H-cyclopropa[e]pyrazolo[1,5-a]pyrimidine ( 16 ), which are related analogs of 1a,b , is also described.     

Ring transformation of 6H-cyclopropa[e]pyrazolo[1,5-a]pyrimidine. VI. Substituent effect of 6-substituted 5a-acetyl-6a-ethoxycarbonyl-5a,6a- dihydro-6H-cyclopropa[e]pyrazolo[1,5-a]pyrimidine-3-carbonitriles

Synthesis and reactivity of 6-ethoxycarbonyl-, 6-phenyl- and 6-methyl-5a-acetyl-6a-ethoxycarbonyl-5a,6a-di-hydro-6H-cyclopropa[e]pyrazolo[1,5-a]pyrimidine-3-carbonitriles 4 , 5 , and 7 are described.     

Aromatization of tetrahydrocyclopropa[a]naphthalenes: An alternative synthesis of 1H-Cyclopropa[a]naphthalene

1H-Cyclopropa[a]naphthalene ( 1a ) is accessible via reduction of the dichloro compound 1c with LiAlH₄/AlCl_3. Several derivatives of tetrahydrocyclopropa[a]naphthalene were synthesized. However, contrary to their 1,1-dihalogeno analogues, they afforded no cycloproparenes upon attempted aromatization.     

Synthetic protocols, molecular polarity, and 13C NMR correlations for 1-aryl- and 1-diarylmethylidene-1H-cyclopropa[b]naphthalenes

The Peterson olefination for alkylidenecycloproparene synthesis from a 1,1-disilylcycloproparene has been refined into five distinct protocols that have provided 43 new aryl- (5 and 6) and diaryl- (7 and 8), and aryl(phenyl)- (9 and 10) methylidene derivatives. The permanent dipole moments of these and other previously reported compounds have been measured and the direction of the dipole, to or from the cycloproparenyl moiety, established for each compound. The 13C NMR spectra are fully assigned and linear correlations of carbon chemical shift with the Hammett sigmap+ constants for each atom within the cycloproparene moiety are provided for the 8-11 compounds that comprise each substitution pattern present in 5-10.     

Dicyclobuta[de,ij]naphthalene and dicyclopenta[cd,gh]pentalene: a theoretical study

The structures, energetics, and aromatic character of dicyclobuta[de,ij]naphthalene, 1, dicyclopenta[cd,gh]pentalene, 2, dihydrodicyclobuta[de,ij]naphthalene, 3, and dihydrocyclopenta[cd,gh]pentalene, 4, have been examined at the B3LYP/6-311++G//B3LYP/6-31G level of theory. All molecules are bowl-shaped, and the pentalene isomers, 2 and 4, are most stable. A comparison with other C(12)H(6) and C(12)H(8) isomers indicates that 2 is approximately 25 kcal/mol less stable than 1,5,9-tridehydro[12]annulene and 4 is approximately 100 kcal/mol higher in energy than acenaphthylene, both of which are synthetically accessible. The transition state structure for bowl-to-bowl inversion of 1 is planar (D(2)(h)()) and lies 30.9 kcal/mol higher in energy than the ground state; the transition state for inversion of 2 is C(2)(h)() and lies 46.6 kcal/mol higher in energy. Symmetry considerations, bond length alternations, and NICS values (a magnetic criterion) all indicate that the ground states of 1, 3, and 4 are very aromatic; however, HOMA values (a measure of bond delocalization) indicate that 3S and 4S are aromatic but that 1S is less so. NICS values for the ground state of 2 strongly indicate aromaticity; however, bond localization, symmetry, and HOMA values argue otherwise.     

Heterocyclic cycloproparenes: 5H-cycloprop[f]isobenzofuran and 5H-cyclopropa[f][2]benzothiophene

The title compounds have been prepared from the Diels - Alder adducts of 1,2-dibromocyclopropene with 3,4-bis(methylene)-tetrahydrofuran and 3,4-bis(methylene)-tetrahydrothiophene by a sequence involving dehydrogenation and dehydrobromination.     

Pendular rearrangement of epimeric 3b,4,4a,5-tetramethyl-3b,4,4a,5-tetrahydro-4H-cyclopropa[a]phenalen-5-yl cations

The kinetics of degenerate pendular rearrangement of 3b,exo-4,4a,5-tetramethyl-3b,4,4a,5-tetrahydro-4H-cyclopropa[a]phenalen-5-yl cation and its endo epimer, generated under conditions ensuring their long life, were studied by dynamic NMR spectroscopy. The rearrangement mechanism is discussed with account taken of the results of quantum-chemical calculations and published data for related rearrangements.     

Arene imine derivatives of nitrogen heterocycles: 1a,9b-dihydrobenz[h]-azirino[f]quinoline, 1a,9b-dihydrobenz[f]azirino[h]quinoline and 1a,9b-dihydroazirino[f][1,10]phenanthroline

The syntheses of the K-imine derivatives of benzo[h]quinoline ( 1 ), benzo[f]quinoline ( 2 ) and 1,10-phenanthroline ( 3 ) are described. The parent nitrogen heterocycles were oxidized with sodium hypochlorite to the corresponding K-oxides, 4, 6 and 8 , which in turn were reacted with sodium azide. The resulting azido alcohols were then cyclized with triethyl phosphite to the title compounds 5, 7 and 9 . The oxirane ring cleavage in benzo[h]quinoline 5,6-oxide ( 4 ) and in benzo[f]quinoline 5,6-oxide ( 6 ) by sodium azide proceeded by the predicted regioselectivity: 4 gave trans-5-azido-5,6-dihydro-6-benzo[h]quinolinol ( 11 ) and trans-6-azido-5,6-dihydro-5-benzo[h]quinolinol ( 10 ) as the major and minor products respectively, and 6 yielded solely trans-6-azido-5,6-dihydro-5-benzo[f]quinolinol ( 12 ). The latter compound proved by X-ray analysis to crystallize as a hydrogen bonded dimer.