Cyclohepta-1:3-diene

The intermediacy of the radical cations of isotoluenes (methylenecyclohexadienes) and their derivatives is a common feature in organic mass spectrometry however, it is widely ignored because of the rather difficult experimental access to neutral isotoluenes. Again, the reader is referred to the discussion on methylenecyclohexadienes in the 1990 review on ionized alkylbenzenes7. An early paper by Lifshitz and Bauer150 on mass spectrometry of bicyclo[3.2.0]hepta-2,6-diene, another C7H8 isomer, as well as of bicyclo[3.2.0]hept-6-ene and one of its isomers, cyclohepta-1,3-diene, may also be mentioned in this context. 

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-formates 187 (R = Me or Bn) (equation 110)103. 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)104. Similarly, periodate oxidation of the optically active hydroxamic acid 203 in the presence of cyclopentadiene, cyclohexa-1,3-diene and cyclohepta-1,3-diene affords chiral products 204 (n = 1, 2 and 3, respectively) in 70-88% yields and 87-98% de (equation 113)105. 

Schenck and Ziegler170 obtained the naturally occurring endoper-oxide ascaridole (166) by irradiation of an alcoholic solution of a-terpinene in the presence of eosin. Endoperoxides similar to 166 are formed in the photosensitized autoxidation of cyclopentadiene,182 cyclohexa-1,3-diene,179,182 cyclohepta-1-3-diene,183 and their phenyl-... 

A cyclic diene for example, cyclohexadiene, cyclohepta 1,3- diene, etc. 

Ruthenium(II) complexes may also be used to oxidize N-Boc hydroxylamine in the presence of tert-butylhydroperoxide (TBHP) to the corresponding nitroso dieno-phile, which is subsequently trapped by cyclohexa-1,3-diene to give the hetero Diels-Alder adduct (Entry 1, Scheme 10.26) [51]. A triphenylphosphine oxide-stabilized ruthenium(IV) oxo-complex was found to be the catalytically active species. Use of a chiral bidentate bis-phosphine-derived ruthenium ligand (BINAP or PROPHOS) result in very low asymmetric induction (8 and 11%) (Entry 2, Scheme 10.26). The low level of asymmetric induction is explained by the reaction conditions (in-situ oxidation) that failed to produce discrete, stable diastereomerically pure mthenium complexes. It is shown that ruthenium(II) salen complexes also catalyze the oxidation of N-Boc-hydroxylamine in the presence of TBHP, to give the N-Boc-nitroso compound which can be efficiently trapped with a range of dienes from cyclohepta-1,3-diene (1 h, r.t., CH2CI2, 71%) to 9,10-dimethylanthracene (96 h, r.t., CH2CI2,... 

The reaction conditions are similar to those employed in the diacetoxylation reaction, with the difference that the halide concentration (usually CI ) has been increased. Thus, palladium-catalyzed oxidation of 1,3-dienes with / -benzoquinone in the presence of lithium chloride and lithium acetate gives l-acetoxy-4-chloroalk-2-enes [78]. For example cyclohexa-1,3-diene and cyclohepta-1,3-diene afforded the corresponding chloroacetates 58a and 58b in good yield and >98% cis selectivity [Eq.(41)]. Cycloocta-1,3-diene gave a 61% yield of acetoxychlorination product (>98% cis), but in this case a 3 1 mixture of 1,4-and 1,2-addition products was formed. A number of substituted cyclic conjugated dienes work well, and, in all cases tried, the reaction proceeds with >97-98% cis selectively [52,78-81]. 

While solvolysis of 5-(4-bromophenylsulfonyloxy)cycloheptene in either acetic acid or tri-fluoroacetic acid after lithium aluminum hydride reduction gave cyclohept-4-enol (71%), cy-clohept-3-enol (12%) and cyclohepta-1,3- and -1,4-diene (5 and 12%, respectively), in contrast acetolysis of 4-(4-bromophenylsulfonyloxy)cycloheptene gave, after saponification with sodium hydroxide in methanol/water, a 78 22 mixture of endo- and exo-bicyclo[4.1.0]heptan-2-ol (1) in 74% yield. Solvolysis of 3-bromocycloheptene afforded, after lithium aluminum hydride reduction, cyclohept-2-enol (37%) and cyclohepta-1,3-diene (63%). ... 

In general, the reaction is not stereoselective and EjZ mixtures of isomers are obtained. Thus, l,l-dichloro-2,3-diethylcyclopropane (11) yielded a 1 1 synjanti mixture of l-ethylidene-2-vinylcyclopropane (12). This example also illustrates the effect of reaction time on the products. Product 12 is obtained in 80-90% yield after 30 minutes at 25 °C. After 2.3 h of reaction time, however, the yield is drastically reduced by isomerization to 1,2-divinylcyclopropane (13) and a subsequent Cope rearrangement of the cw-isomer of 13, followed by isomerization, to cyclohepta-1,3-diene (14). Higher reaction temperatures also lead to rearrangements. ... 

A cycloheptenone precursor to the (+)-Prelog-Djerassi lactonic acid has been synthesized stereoselectively from cyclohepta-1, 3-diene using a nucleophilic addition-reactivation-nucleophilic addition sequence on iron complexes to introduce the required... 

Bridged Peroxides.—Routine procedures have been extended to the synthesis and characterization of photo-adducts of singlet oxygen with cyclo-octa-1,3,5-triene, cycloheptatrienes, 3,5-cycloheptadienone, cyclohepta-1,3-dienes, ° naphthalenes, anthracenes, a-pyrones, pyrazines and pyrimidines,imidazoles, and indenes. Transformation of some of these... 

Cycloheptatriene does not react with Fe(CO)s to give the expected dicarbonyl complex 7i -C7H8Fe(CO)2, but forms instead a mixture of tricarbonyl complexes derived from cycloheptatriene and cyclohepta-1,3-diene (20, 35). This work, together with protonation and related reactions of the free double bond of 7r-C7HsFe(CO)3, have been summarized by Pettit and Emerson (118). More recently, Pettit and co-workers (101) have shown that (7-methoxycycloheptatriene)Fe(CO)3 is protonated by fluoro-boric acid with loss of methanol to give the ir-tropylium-iron tricarbonyl cation. 

Relatively little work has been done on complexes of cyclohepta-1,3-diene, and almost none on complexes of the 1,4-isomer. The iron tricarbonyl complex l,3-C7HioFe(CO)3 is obtained from Fe(CO)s and the diene, and also from Fe(CO)5 and cycloheptatriene 19,35). More recently, a complex of zero-valent iron containing only cyclohepta-l,3-diene and cycloheptatriene, has been obtained by a reductive Grignard reaction on ferric chloride (57). 

Nothing is known about the chelating tendencies of cydoocta-l,3-diene and cycloocta-1,4-diene with platinum(II). Methanolic Na2PdCU reacts with the 1,3-diene at room temperature to give a methoxy-substituted ir-allyl complex, while on heating ir-cycloocta-2,4-dienylpalladium(II) chloride is formed 122). The latter is also obtained from the diene and PdCl2 in acetic acid 82). Both complexes are similar to their cyclohepta-1,3-diene analogs (Section II, D). 

Naphthyne has been condensed with ketone enolates, including those of mediumring ketones, to give mixtures of ((i-naphthyl)-2-cyclic ketones and naphtho[l,2]-cyclobutenols. Reactions of cycloheptatriene, cyclohepta-1,3-diene, and cyclo-heptene with benzyne have been studied e.g. cycloheptatriene gives a mixture of 8,9-benzo-cis-bicyclo[5,2,0]nona-2,4,8-triene and 7-phenylcycloheptatriene. ... 

Irradiation of cycloheptene in the presence of mercury gave a mixture of norcarane, vinylcyclopentane, hepta-1,6-diene, and other minor products. Deuterium labelling showed that the norcarane arose via a 1,2-hydrogen shift followed by ring-closure. The photochemical conrotatory ring-closure of all possible 1,3-dimethyl- and 1,4-dimethyl-cyclohepta-1,3-dienes has been carried out. " ( )-Grandisol has been synthesized from eucarvone, the first step in the synthesis being the photoisomerization of eucarvone to l,4,4-trimethylbicyclo[3,2,0]hept-6-en-2-one. °... 

Bromination of cyclo-octa- and cyclohepta-1,3-dienes has been found to result in homo-1,4-addition, giving 2,6-dibromobicyclo[5,l,0]octane and 2,5-dibromobi-cyclo[4,1,0]heptane, respectively, in contrast to earlier claims. ... 

The alkoxy ir -allylic derivatives underwent alkoxyl exchange very readily when treated with the appropriate alcohol containing a little mineral acid (10" M)(e.g. methoxy-ethoxy and vice versa). These reactions are believed to go via an intermediate carbonium ion stabilised by the delocalised electron system of the tt-allylic group. Methoxy tt-allylic complexes derived from 2,5-dimethylhexa-2,4-diene, cyclohepta-1,3-diene and cycloocta-1,3-diene on heating lost methanol irreversibly to give a8-unsaturated tr-allylic complexes e.g. cyclohepta-1,3-diene first gave a tt-methoxycycloheptenyl and then a TT -cycloheptadienyl complex. 

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