Cyclohexa-l,2-diene

The complexation of 2b in the presence of 12.5 mol% of the azadiene catalyst 4 provides quantitatively tricarbonyl[r] -cyclohexa-l,3-diene]iron 5... 

An alternative method for the oxidative cyclization of the arylamine-substituted tricarbonyl(r -cyclohexa-l,3-diene)iron complex (725) is the iron-mediated arylamine cyclization. Using ferricenium hexafluorophosphate in the presence of sodium carbonate provided hyellazole (245) directly, along with the complex 727, which was also converted to the natural product (599,600) (Scheme 5.71). 

We reported the first total synthesis of l,T-bis(2-hydroxy-3-methylcarbazole) (213) using our molybdenum-mediated construction of the carbazole framework (560). The required monomer, 2-hydroxy-3-methylcarbazole (52), was obtained in three steps, and 22% overall yield, starting from dicarbonyl(ri -cyclohexa-l,3-diene)(ri -cyclopentadienyl)molybdenum hexafluorophosphate (663) and 3-meth-oxy-4-methylaniline (655) (560) (see Scheme 5.52). Finally, oxidative coupling of the monomer 52 using p-chloranil afforded l,T-bis(2-hydroxy-3-methylcarbazole) (213) in 38% yield (560) (Scheme 5.167). 

Whereas the hexa-1,3,5-triene/cyclohexa-l,3-diene rearrangement serves as a model reaction in the hydrocarbon series, the perfluoro analog behaves differently, as presented in Section 5.3.2.1. Photolysis of perfluorohexa-l,3,5-triene (8) in the gas phase yields per-fluorobicyclo[2.2.0]hex-2-ene (10) as the major product, presumably via perfluorocyclohexa-1,3-diene (9).4 Perfluoro(3-vinylcyclobutene) is formed as the minor product. Thermolysis of hexa-tricnc 8 gives cyclohexadiene 9.4 Photolysis of 9 provides bicyclohexene 10, which reverts to 9 thermally.5... 

Hammond et al. (309), die ebenfalls die photosensibilisierte Dimerisation des Cyclohexa-l,3-diens untersuchten, haben darauf Mngewiesen, daB diese Umlagerungen allein noch nicht zwischen den Strukturen 33, 37 und 38 bzw. 34, 39 und 40 entscheiden. Fur das Hauptprodukt konnte Struktur 33 durch Hydrierung zum gesattigten Kohlenwasserstoff 41 bewiesen werden, der auch aus dem Photodimeren 42 des Cyclohexenons... 

Fur das bereits seit 1955 bekannte l l-Addukt des Durochinons an Cyclohexa-l,3-dien konnte kurzlich die Kafigstruktur 92 bewiesen werden (162,163). 

Scheme 56 Cl-cycloaddition-cyclocondensation three-component synthesis of l-acetyl-2-amino-cyclohexa-l,3-dienes 104...

The efficient trapping of the cyclohexadienyl anionic intermediates with protons raises the possibility of qnenching with carbon electrophiles. The process is not as general as the proton quench. However, when the nucleophile adds essentially irreversibly, quenching with a limited set of carbon electrophiles is successful. For example, addition of 2-lithio-l,3-dithiane to benzene-Cr(CO)2T, followed by addition of ethyl iodide and then oxidation or addition of a donor ligand (CO, PhsP), produces a cyclohexa-l,3-diene substituted by both acetyl (Me + CO) and the nucleophile (Scheme 47).134,209 insertion of CO occurs, without... 

The earliest reduction reactions of arene oxides to be reported involved catalytic hydrogenation of 1 (H2-Pd) to yield oxepane and reaction with lithium aluminium hydride to give cyclohexa-l,3-dien-5-ol. An alternative type of reduction reaction... 

The benzene cyclohexa-l,3-diene complexes (CgHg)(l,3-CgHg)M (M = Fe, Ru, Os) have been prepared by reacting the metal trichlorides with i-PrMgBr in the presence of 1,3-CgHa 143, 144). The iron and... 

The quenching kinetics of 02( Ag) by the colourless trap cyclohexa-l,3-dien-... 

Cyclohexa-l,3-dien-5-one—see o-Isophenol Cyclohexadienones 1035—see also 4-AIkoxycyclohexadienones, Halocyclohexadienones, o-Isophenol, Nitrocyclohexadienones heats of formation of 40 ionized 264, 265 synthesis of 1080, 1082... 

The structure of the complex formed from tricarbonyl(isoprene)iron and hexafluoropropene has been established crystallographically as [77], allowing the assignment of the parameters shown with the structure, and similar assignments for the products from the butadiene- and 2,3-dimethylbutadiene-tricarbonyliron complexes then follow. (49) With tricarbonyl(cyclohexa-l,3-diene)iron, hexafluoropropene gave [78], in... 

In some cases the method chosen for dehydration has a decisive effect on the outcome of the reaction. Thus, the adduct of 4,4-dimethylcyclohex-2-enone underwent dehydration with (methoxycarbonylsulfamoyl)triethylammonium hydroxide, inner salt (Burgess reagent) in refluxing benzene to give 5,5-dimethyl-2-[l-(phenylsulfanyl)cyclopropyl]cyclohexa-l,3-diene (5) in 93% yield. 

Acylnitroso compounds 197 (R = Me, Ph or Bn) react in situ with 1-methoxycarbonyl-1,2-dihydropyridine to yield solely the bridged adducts 198 quantitatively. On the other hand, 1 1 mixtures of the regioisomers 199 and 200 were formed from the nitroso-foimates 187 (R = Me or Bn) (equation 110) ° . The chiral acylnitroso compounds 201 and 202, which are of opposite helicity, add to cyclohexadiene to give optically active dihydrooxazines in greater than 98% diastereomeric excess (equations 111 and 112) °. Similarly, periodate oxidation of the optically active hydroxamic acid 203 in the presence of cyclopentadiene, cyclohexa-l,3-diene and cyclohepta-l,3-dicne affords chiral products 204 (z = 1, 2 and 3, respectively) in 70-88% yields and 87-98% de (equation 113) ° . 

The chiral A-sulfinylcarbamate 248 derived from 8-phenylmenthol formed a mixture of two epimeric cycloadducts 249 and 250 with cyclohexa-l,3-diene (equation 132)", whereas the reaction with ( . )-hexa-2.4-diene in the presence of tin(IV) chloride gave solely the epimer 251 (equation 133)"- . 

Diethyl azodicarboxylate fonns normal adducts with 2,3-dimethylbutadiene and with ethyl sorbate however, it is not a very good dienophile, presumably because it exists in the fraw5-configuration. The sterically hindered diene 254 adds the ester to give mainly the ene product 255 (equation 137) and even cyclohexa-l,3-diene undergoes an analogous... 

For instance, the reaction of cyclohexa-l,3-diene and ethyl glyoxylate in the presence of (S)-31 proceeds smoothly to give the cycloadduct in 66% yield with 97% ee. The synthetic application of this process was demonstrated by the preparation of a highly interesting synthon for sesquiterpene lactones in high yield and diastereoselectivity, and with a very high ee as illustrated in Scheme 17 [35]. 

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