Hexa-1,2,4,5-tetraene

An example is the synthesis of substituted [2.2]paracyclophanes as reported by Hopfet al When hexa-1,2,4,5-tetraene 23 is treated with dimethyl acetylenedi-carboxylate 24 (an electron-poor acetylenic dienophile), the initially formed reactive intermediate 25 dimerizes to yield the [2.2]paracyclophane 26 ... 

Radiolysis of the diacetylene hexa-l,5-diyne (50) generates the hexa-1,2,4,5-tetraene radical cation (51 +) via a Cope rearrangement in the Freon matrix. ... 

The skeletal rearrangement of various strained cyclic compounds is carried out with a catalytic amount of soluble complexes of PdCl2. Namely, the rearrangements of bulvalene (67) to bicyclo[4.2.2]deca-2,4,7,9-tetraene (68)[54], cubane (69) to cuneane (70)[55], hexamethyl Dewar benzene (71) to hexa-methylbenzene (72)[56], and 3-oxaquadricyclanes[57] and quadricyclane (73) to norbornadiene[58-60] take place mostly at room temperature. Reaction of iodocubane (74) with a terminal alkyne catalyzed by Pd(0) and CuBr unexpectedly affords an alkynylcyclooctatetraene 75, without giving the desired cubylalkyne 76. Probably the rearrangement is a Pd-catalyzed reaction[61]. 

To demonstrate the quality of this simple approach we show in Figures 6 and 7 the PE spectra of 1,3-butadiene 2, (3 )-hexa-l,3,5-triene 161, (3E, 5 )-ocla-1,3,5,7-tetraene 234, [3]radialene 173, 3,4-dimethylidenecyclobutene 174 and fulvene 175. The observed positions I j1 of the tt-bands are collected in the third column of Table 2, and the eigenvalues xj obtained from standard HMO models in the fourth. A least-squares calculation yields the linear regression... 

Dienes react with molybdenum hexacarbonyl to give complexes of the type [Mo(CO)4(diene)] and [Mo(CO)2(diene)2], which are generally yellow, soluble in organic solvents, and readily sublimed. Cyclo-octa-1,5-diene (12, 79, 151), bicyclo[2,2,l]hepta-2,5-diene (175), a dimer of cyclo-octa-tetraene (12) and dimethyldivinylsilane (158) give the former type of complex with the structure (VI M = Mo), while butadiene (81) and cyclo-hexa-1,3-diene form the latter type (80). Tetracyclone gives the complex [Mo(CO)2(tetracyclone)2] (215). 

Dithia, 12,14.15-triaza-penta-cyclo[9.3.1.13-9.02 °.04, ]hexa-deca-llS,5,11,13-tetraen ... 

CuFi2N4P2C24H28, Copper(II), (2,9-dimethyI-3,10-diphenyl-l, 4,8,11 -tetraazacyclotet-radeca-l,3,8,10-tetraene)-, bis[hexa-fluorophosphate(l-)], 22 10 Cul, Copper iodide, 22 101 CuN307SC,3H,4, Copper(II), (1,10-phenan-throline)[serinato(l-)]-, sulfate, 21 115 CUN4O2C10H18, Copper(II), [1,4,8,11-tetra-zacyclotetradecane-5,7-dionato(2-)]-, 23 83... 

F,N,NiP2C4jH4, Nickel(II), [3,ll-bis(a-(benzylamino)benzylideneI-2,12-di-methyl-1,5,9,13-tetraazacyclohcxadeca-1,4,9,l2-tetraene-KWbis[hexa-fluorophosphate( I -)], 27 276... 

FtPjRuCwHn. Ruthenium(ll), (tf-cyclo-pentadienyl)(phenylvinylene)bis-(triphenylphosphine)-, hexa-fluorophosphate(l -), 21 80 FuFehyCaHn, Iron(U), bis(acetonitrile) (2,9-dimethyl-3,10-diphenyl-1,4,8,11 -tetraaza-cyclotetradeca-1,3,8,10-tetraene)-, bis[hexafluorophosphate(l —)], 22 108 F,2Fe2N2P2S2C, H36, lron(2 + ),... 

Fused stiboles (123 R = Me) have also been prepared by this chemistry (Scheme 26). However, on attempted preparation of the bismole (113), the tetraene (51) is the major product. Bismole (113) is only observed by H NMR <93ACS(47)326>. There is a thermodynamic preference for formation of the tetraene since the bismole (113) is stable when prepared from the dianion and PhBiX2. Reaction of the zirconacycle (122 R = TMS) with either PhSbCl2 or PhBiCl2 provides neither heterole (113 R = TMS), (123 R = TMS), nor the tetraene, but instead gives the zirconacycle precursor 1,6-bis(trimethylsilyl)hexa-l, 5-diyne. 

The size of the K-system chosen has important implication on the structural and functional aspects of metal binding. To explore the size effect calculations were performed on the cation-ir complexes of Li+ and Mg + with the Jt-face of linear and cyclic unsaturated hydrocarbons [45]. In the case of the acyclic Jt-systems, we started with the simplest system, e.g. ethylene followed by buta-1,3-diene, hexa-l,3,5-triene, and octa-1,3,5, 7-tetraene with 2, 3 and 4, conjugated jt units, respectively. These linear systems with two and more number of jt units can have various conformations wherein the jt units can have cis, trans or a combination of both cis and trans orientations. Similarly for cyclic systems cyclobutadiene, benzene, cyclooctateraene, naphthalene, anthracene, phenanthrene and naphthacene have been included. Thus a wide range of sizes for aromatic systems have been covered. 

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