Benzvalene synthesis

Abstract

Among interesting chemical structures, that of the valence isomer of benzene, benzvalene (I), is one of the most fundamental and one of the rarest. Benzvalene has been synthesized by photolyzing benzene,1,2 but because its photochemical decomposition is benzene sensitized,lb the steady-state concentrations do not exceed 0.05 %,la and although the conversion can be increased to 1 % by dilution with hexadecane,13 the yield is still small and the product diluted by solvent. We are reporting a simple procedure for synthesizing the benzvalene ring system that makes this rare hydrocarbon abundant. IIThe procedure is indicated in reaction 1. Reasons for expecting its efficacy have been enumerated pre-++ CHA + CH3Li + (^) (1) viously,3 but the best reason is that the analogous reaction works, using the cyclononatetraenyl anion,3•4 and gives as the major product isobullvalene (II), the corresponding valence tautomer of cyclodecapentaene.An important consideration in effecting the reaction is the choice of solvent, as carbonoid reactions of lithium halomethides occur best in those that solvate lithium cations poorly.3 However, the commonly used solvent, diethyl ether,3,3af' does not dissolve lithium cyclopentadienide. By contrast, dimethyl ether does, and if reaction 1 could be effected using it, the isolation of large quantities of benzvalene would be easy because distillation should separate it from the much lower boiling solvent. In fact, reaction 1 can be effected in dimethyl ether and gives a 24% yield of benzvalene,7 samples of which were isolated pure and identified by proton nmr spectroscopy. However, we were discouraged from investigating its large-scale isolation pure when the resonance energy of benzene and the strain energy of small-ring compounds were called to our attention by the benzvalene exploding.8•9(1) (a

Thermal and photochemical generation of electronically excited organic molecules. Tetramethyl-1,2-dioxetane and naphthvalene

“…Katz, Wang and Acton 40 have recently reported a brilliant synthetic route to benzvalene (XXI) and naphthvalene (XXII). In a collaborative effort, we have examined the thermolysis and photolysis of XXI and XXITin a spectrophotofluorimeter, to determine if electronically excited products are produced.…”

Crystal Structure Determination of the Pentagonal‐Pyramidal Hexamethylbenzene Dication C6(CH3)62+

“…[1,2] Chemists have long been fascinated by finding exceptions from these rules.S tarting in the 1960s,v alence isomers of benzene were prepared through elaborate organic syntheses, [3][4][5][6] while hypercoordinated carbon compounds entered the stage through the pioneering work of Olah on superacids and non-classical cations. [7,8] Theb onding situation in protonated methane (CH 5 + ), which is the most prominent representative of pentacoordinated carbon, is best described as a3-center 2-electron bond between H 2 and CH 3 + ,but its isolation in bulk is elusive.The replacement of hydrogen with organogold species lead to the isolation of penta-and hexacoordinated methanium salts by Schmidbaur.T hese carbido clusters,[ (Ph 3 PAu) 5 …”

4-(Phenylsulfanyl)tricyclo[3.1.0.02,6]hexan-3-one: Synthesis, Alkylation, and Base-Induced Dimerisation

“…There is a precedent for the postulated isomerisation of To a stirred solution of benzvalene (4) [14] (102 mmol, 175 ml 7 to 13. On exposure to hot aqueous sodium hydroxide, the 0.583  in ether), cooled to Ϫ78°C, a solution of phenylsulfenyl tricyclohexanone 2 rearranges to the bicyclohexenone chloride [15] (14.7 g, 102 mmol) in dichloromethane (250 ml) was…”