L 41-bicyclo hexene

A further alternative route to the intermediate (8 R = H) has been outlined in a patent by the Upjohn group. This synthesis starts with the bicyclo[3,l,0]hexenal (36), which is converted into (8 R = H) via the key intermediate (37) as outlined in Scheme 6. The route is closely similar to one of Corey s earlier schemes to total PG synthesis and has been applied to the synthesis of the and Faa PG s in addition to the Eg- and F2 -series. 

Some of the bicyclo[3.1.0]hexene zirconocene derivatives, especially those containing a phenyl group, rearrange quantitatively to the corresponding 4-vinyl-l-metalla-2-cyclobutene derivatives when heated in toluene to 60-80 °C for several hours (equation 131). The 6,6-dimethyl-2,3-diphenyl-2-zirconabicyclo[3.1.0]hex-3-ene derivative prefers ring-opening to the isomeric j/. -allylic complex upon thermolysis. 

Cyclopropene can also be used as the aUcene component and affords bicyclo[3.1.0]hexen-2-ones upon reaction with alkyne dicobalt octacarbonyl complexes in the presence of NMO (Scheme 250). Vinyl ethers and vinyl esters serve as ethene equivalents in Pauson-Khand reactions. For example, reaction of vinyl benzoate with complex (169) furnished cyclopentenone (170) (Scheme 251). This reaction was used in a synthesis of (-l-)-taylorine and nortaylorine. Allenes participate in intermolecular Pauson-Khand reactions affording alkylidene-substituted cyclopentenones (Scheme 252). ... 

Five-membered rings have tilso been obtained from unsaturated alkyl azides. Heating of 5-azido-5-methyl-l-hexene (149) yielded a mixture of 2,5,5-trimethyl-1-pyrroline (151) and 2,2-dimethyl-1-aza-bicyclo[3,l,0]hexane (152) (total yield 70%, products ratio 2-2 1). This reaction however proceeds via the isolable triazoline 150 and no nitrene intermediates are involved... 

Aus l,l-Dimethyl-l,2-dihydro-naphthalin entstehen photolytisch bei—100° (2-Isopropyl-phenyl)-allen, 2-Isopropenyl-l-propen-(2)-yl-benzol und 6,6-Dimethyl-(benzo-bicyclo[3.1.0] hexen-(2)y. Bei 20° vvird iiber l-(2-Isopropenyl-phenyl)-propen in eincr wcitcrcn Photo-reaktion 1,6-l)imethyl-(benzo-bicyclo[3.1.0]hexen-(2)y gebildet2 4. Anhand der deuterierten Verbindung wird dieser Mochanismus geklart ... 

Diphenyl-3- methylen-cyclo- hexadien-(l,4) 4 g in 750 ml tert. -Butanol 22,2 mEinstein einer Hg-Hoehdruck-Lampe Filter durchlassig fiir A = 230-315 u. 320-355 nm l,endo-6-Diphenyl-4-methylen-bicyclo [3.1,0]hexen-(2)e 11.7 3... 

Effizienz (

[Pg.438]

Eino l%ige Losung von 3-Hydroxy-4-oxo-2,6-dimethyl-4H-pyran in Methanol liefert. nach 2,5 Stdn. (450 W Hanovia Corex-Eilter StickstofF) cin l l-Gemisch (F 150-165°) aus 5-Hydroxy-3,4-dioxo-l, 5-dimMh.yl-cyclopenten und 5-Hydroxy-4-oxo-1,2-dimethyl-6-ooca-bicyclo [3.1,0]hexen-(2)3 ... 

Bei der 4fach phenylierten Verbindung entsteht in einem weiteren photochemischcn Schritt l,3-Diphenyl-2,3-dihydro-l I- cyclopenta-[l]-phenanthreny (5% d.Th.). Das Acetat von 4-Hydroxy-l,2,3,5-tetraphenyl-bicyclo[3.1.0]hexen-(2) liefert dagegen ausschlieBlich 1,2,3,3-Tetraphenyl-benzol (70% d.Th.). 

Im Falle des 4-0xo-l,2,3,5-letruplieiiyl-6-oxu-bicyclo[3.1.0]hexen-(2) kann das entsprechende Pyry-ium-Salz als l crchlorat3 (F 278-279°) abgefangen werden. 

Oxo-l,7-diphenyl-(benzo-6-oxa-bicyclo[3.1.0]hexen-(2)) in50 ml frisch destiliertem Bicyclo[2.2.1]hepta-dien wird in einem wassergekiihlten QuarzgefaB mit einer 100 W Quecksilber-Mitteldruck-Lampe 5 Stein, bestrahlt. AnschlicBend wird das iibersehiissige Bicyclo[2.2.1]heptadien i. Vak. entfernt und der Buck-stand mit 25 ml heiBem Athanol zerrieben Ausbeute 0,83 g (63% d.Th.) F 215-216° (Athanol). 

A diazo transfer reaction takes place, however, between diazoalkanes and derivatives of cyclopropene. Thus, in the reaction of dimethyl 3,3-dimethyl-cyclo-propene-l,2-dicarboxylate (2.200) with diazomethane, the primary product 2.201, a diaza bicyclo[3.1.0]hexene, isomerizes on irradiation to the diazo compound 2.202 (2-79). Acid catalysis, however, leads to the isomerization of 2.201 to the 1,4-dihydro-pyridazine 2.203 (Franck-Neumann and Buchecker, 1969). An analogous reaction of... 

In 2006, Gagosz reported the cycloisomerisation of 5-en-2-yn-l-yl acetates to acetojy bicyclo[3.1.0]hexenes at room temperature. Propargylic acetates bearing different substitutions were successfully cyclised in the presence of 1 mol% of complex XXX in dichloromethane. The reaction proceeded smoothly at room temperature and short reaction times were required. The authors showed that these complexes could be used as precursors to synthesise cycloenones when they were treated with catalytic amounts of base in methanol. In addition, when the solvent was changed from dichloromethane to methanol a cyclohexene molecule was obtained, which could be further converted to 2-cyclohexen-l-one. This product is a regioisomer of the cyclohexenones obtained using the first route (Scheme 16.66). 

There are many examples of preparing cyclopentane structures from enynes by gold-catalyzed carbocyclization reactions. Toste et al. have reported that Au(l)-phosphine complexes act as superior catalysts for isomerization of 1,5-enynes to bicyclo[3.1.0]hexenes [124]. For example, treatment of 1,5-enyne (86) with 1 mol% of PhsP-AuPFfi in dichloromethane at room temperature results in formation of cyclopropane-fused cyclopentene (87) in 99% yield (Scheme 18.30). 1,6-Enynes also undergo similar cycloisomerization to five-membered cyclic compounds under the influence of cationic gold(l) catalysts [125, 126], Hydroxylated enynes are versatile precursors for cyclopentenones by gold-catalyzed cycloisomerization... 

Buzas, A., Gagosz, F. (2006). Gold(I) catalyzed isomerization of 5-en-2-yn-l-yl acetates an efficient access to acetoxy bicyclo[3.1.0]hexenes and 2-cycloalk en-l-ones. Journal of the American Chemical Society, 128,12614-12615. 

Marion, N., de Fremont, R, Lemrere, G., Stevens, E., Fensterbank, L., Malacria, M., Nolan, S. (2006). Au(I)-catalyzed cycloisomerization of 1,5-enynes bearing a propar-gylic acetate formation of unexpected bicyclo[3.1.0]hexene. Chemical Communications, 2048-2050. 

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