Stereochemistry of aziridine formation from ketoximes of bridged ring systems by lithium aluminum hydride reduction on benzobicylo[3.2.1]octenone oximes

synthesis of 1-Phenyl -1, 2-Cyclohexadiene and 1-(2-Bromocyclohex-2-En-1-Yl)Benzene and Wurtz-Like Condensation Products in the reaction of 1-(2,3-Dibromocyclohex-1-En-1-Yl) Benzene with Zinc

The base-catalysed elimination of 1-(2-bromocyclohex-2-en-1-yl)benzene 1 and the zinc-catalysed elimination of 1-(2,3-dibromocyclohex-1-en-1-yl)benzene 9 have been used for the synthesis of 1-phenyl-1,2-cyclohexadiene 2; reaction of 9 with zinc in THF resulted in the formation of two isomeric Wurtz-like condensation products 3 and 4, but the reaction of 1 with t-BuOK gave the allene 2.

Photochemical approach to functionalized benzobicyclo[3.2.1]octene structures via fused oxazoline derivatives from 4- and 5-(o-vinylstyryl)oxazoles

Novel cis/trans-4- and cis/trans-5-(2-vinylstyryl)oxazoles have been synthesized by Wittig reactions from the diphosphonium salt of α,α’-o-xylene dibromide, formaldehyde and 4- and 5-oxazolecarbaldehydes, respectively. In contrast, trans-5-(2-vinylstyryl)oxazole has been synthesized by the van Leusen reaction from trans-3-(2-vinylphenyl)acrylaldehyde which is prepared from o-vinylbenzaldehyde and (formylmethylene)triphenylphosphorane. The 4- and 5-(2-vinylstyryl)oxazoles afford, by photochemical intramolecular cycloaddition, diverse fused oxazoline-benzobicyclo[3.2.1]octadienes, which are identified and characterized by spectroscopic methods. The photoproducts formed are relatively unstable and spontaneously or on silica gel undergo oxazoline ring opening followed by formation of formiato- or formamido-benzobicyclo[3.2.1]octenone derivatives. On irradiation of 4-(2-vinylstyryl)oxazole small quantities of electrocyclization product, 4-(1,2-dihydronaphthalen-2-yl)oxazole, are isolated and spectroscopically characterized.

A tetrabromo-1,4-ethanonaphthalene and related dibromo-1,4-ethenonaphthalene

(1RS,3RS,4RS,10SR)-2,2,3,10-Tetrabromo-1,2,3,4-tetrahydro-1,4-ethanonaphthalene, C12H10Br4, (I), is the first structure to be reported with four Br atoms bound to a 1,4-ethanonaphthalene framework and also the first which possesses three Br atoms inexopositions. Interactions between the Br atoms [three short intramolecular Br...Br distances of 3.1094 (4), 3.2669 (4) and 3.4415 (5) Å] have little effect on the C—C bond lengths but lead to significant twisting of the cage structure compared with the parent hydrocarbon, which is expected to be fully eclipsed at the two saturated C2H4bridge positions. Chemically related (1SR,4RS)-2,3-dibromo-1,4-ethenonaphthalene, C12H8Br2, (II), obtained by double dehydrobromination of (I), represents the first structure of any halogen-substituted benzobarrelene. Thiscis-dibromide shows little evidence of steric congestion at the double bond [Br...Br = 3.5276 (8) Å] as a consequence of the large C—C—Br angles [average C=C—Br angle = 126.15 (10)°].

exo-10,11-Dibromo-tricyclo-[6.3.1.0]dodeca-2,4,6,9-tetra-ene

The title compound, C₁₂H₁₀Br₂, is a bridged ring system based on a homobenzonorbornadiene framework. The exo configuration of one of the Br atoms was previously assigned via NMR correlations and has now been confirmed by the geometry of the solid-state structure. The compound features a Br—C—C—Br torsion angle of 66.68 (12)°, whereby the C atoms in the calculation are respectively sp³- and sp²-hybridized.

Generation and trapping of a highly strained bicyclic alkyne: tricyclo[6.3.1.0(2,7)]dodeca-2,4,6-trien-9-yne

High-temperature bromination of 10-bromotricyclo[6.3.1.0(2,7)]dodeca-2,4,6,9-tetraene (8) resulted mainly in the formation of two isomeric tribromides (16 and 17) whose dehydrobromination with DBU afforded the corresponding 9,10-dibromotricyclo [6.3.1.0(2,7)] dodeca-2,4,6,9-tetraene (14). Treatment of 14 with tert-butyllithium in THF at -78 degrees C produces the strained bicyclic alkyne (10) which is trapped by 1,3-diphenylisobenzofuran to give two isomeric cycloadducts 12a and 12b. The adducts 12a and 12b were found to readily rearrange to the isomeric ketones 19a and 19b upon chromatography. Upon treatment with potassium tert-butoxide, the adducts 12a and 12b undergo base-catalyzed double bond isomerization to give four products 20-23. Furthermore, reaction of 14 with one and two mole of potassium tert-butoxide has been studied and the mechanism of the product formation is discussed with regard to either an allene or alkyne as a possible intermediate.