Cycloheptatriene derivatives

The thermal decomposition of diazo(phenylsulfonyl)methane 223 under a nitrogen atmosphere generates phenylsulfonylcarbene which is trapped by olefin such as cyclohexene to give norcaranes 224 and 225 (equation 138)132. No cycloheptatriene derivative is isolated from the thermolysis of223 in benzene133. In contrast, intramolecular insertion of sulfonylcarbenes into a benzene ring is observed in the thermolysis of 226 (equation 139)134. 

The reaction of alkenylcarbene complexes and alkynes in the presence of Ni(0) leads to cycloheptatriene derivatives in a process which can be considered as a [3C+2S+2S] cycloaddition reaction [125]. As shown in Scheme 77, two molecules of the alkyne and one molecule of the carbene complex are involved in the formation of the cycloheptatriene. This reaction is supposed to proceed through the initial formation of a nickel alkenylcarbene complex. A subsequent double regioselective alkyne insertion produces a new nickel carbene complex, which evolves by an intramolecular cycloprop anation reaction to form a nor-caradiene intermediate. These species easily isomerise to the observed cycloheptatriene derivatives (Scheme 77). 

It has been shown how alkenylcarbene complexes participate in nickel(0)-me-diated [3C+2S+2S] cycloaddition reactions to give cycloheptatriene derivatives (see Sect. 3.3). However, the analogous reaction performed with alkyl- or aryl-carbene complexes leads to similar cycloheptatriene derivatives, but in this case the process can be considered a [2S+2S+2S+1C] cycloaddition reaction as three molecules of the alkyne and one molecule of the carbene complex are incorporated into the structure of the final product [125] (Scheme 82). The mechanism of this transformation is similar to that described in Scheme 77 for the [3C+2S+2S] cycloaddition reactions. 

The reaction of troponephenylhydrazone with carbon disulphide afforded the bicyclic thiazole (37) in quantitative yield. iV-methoxytroponimine when treated with phenylisothiocyanate afforded a mixture of cycloheptatriene derivatives (38a) and (38b). Both of these reactions proceed via an [8+2] cycloaddition <95H1675>. 

Starting from 2,4,6-octatriene and pivaldehyde, the conjugated homoallylic alcohol 8 is obtained as the sole product. Cycloheptatriene-derived complexes react with aldehydes and C02 to afford mixtures of the isomeric 1,3- and 1,4-cycloheptadienyl carbinols or acids, respectively. Interestingly, analogous reactions with methyl chloroformate or dimethyl carbamoyl chloride produce the conjugated dienyl ester 9 or amide 10 as unique products [19,20]. 

A similar transformation was observed with the rhodium trifluoroacetate catalyzed decomposition of diazo ketones in the presence of benzene (Scheme 32).130 The cycloheptatrienes (147) formed in this case were acid labile and could be readily rearranged to benzyl ketones (148) on treatment with TFA. The reaction was effective even when the side chain contained reactive halogen and cyclopropyl functionality, but competing intramolecular reactions occurred with benzyl diazomethyl ketone. A more exotic example of this reaction is the rhodium(ll) trifluoroacetate catalyzed decomposition of the diazopenicillinate (149) in the presence of anisole, which resulted in the formation of two cycloheptatriene derivatives (150) and (151) (equation 35).m... 

Four optically active cycloheptatriene derivatives carrying a methoxy group(s) at different positions were prepared by the pentane-2,4-diol-tethered Buchner reaction (g) (Scheme 13).24 In addition to the high stereoselectivity, the tether also controlled the regioselectivity. 

Exposure of tricyclo[4.1.0.02 7]hept-3-enes to catalytic amounts of Ag+ leads instantaneously and quantitatively to cycloheptatriene derivatives.7 Promise of their usefulness as synthetic intermediates is growing rapidly.1314... 

Closely related to these arene carbonyl complexes are the cycloheptatriene derivatives, which, however, are prepared by insertion of C7H8 into a Re-C bond followed by H abstraction, with Ph3C+, as shown in Scheme 32. 

With alkynes as cosubstrates satisfactory yields of cyclotrimers are obtained in the presence of phosphane-free Co(I) catalysts, e.g r 3-cyclooctenyl-r 4-cycloocta-diene cobaltQ). The main products are tricyclo. O.O Joct -ene derivatives 32, sometimes accompanied by small amounts of the norcaradiene/cycloheptatriene derivatives 33 and 34 (Eq. 42)27>. 

This type of double dehydrobromination has also been used in a few syntheses of 1,6-methano-annulated systems in which the initially formed norcaradiene isomerizes to the corresponding cycloheptatriene derivative. Thus, a good yield of bicyclo[4.4.1]undeca-l,3,5,7,9-pentaene (11, X = H) was obtained by treating the corresponding tetrabromide (9, X = H) with methanolic potassium hydroxide. The 11,11-difluoro analog 11 (X = F) was likewise obtained in 80% yield. The 11,11-dichloro (X = Cl) and 11,11-dibromo (X = Br) analogs, however, were ob-... 

Upon heating, the bisthio derivatives underwent sulfur elimination and subsequent ring opening to the corresponding cycloheptatriene derivatives. 

A study of photochemical 1,7-hydrogen migrations within the cycloheptatriene derivatives (127) has been reported. Hansen and his coworkers have demonstrated that irradiation of the heptalenes (128) brings about reversible isomerization into a mixture of isomers composed of (129) and starting material (128). To some extent, the ratio of photo-product starting material is dependent upon the substitution as indicated by the yields shown under the appropriate structure. ... 

The difficulty with the formation of a five-membered aryne is, most probably, the reason for the anomalous course of oxidation of Af-aminotri-azoles 344 and 345, leading to cycloheptatriene derivative 347. Supposedly, the precursor of the latter compound is the unstable tetrazine 346 (85TL335). On the other hand, amine 148, on oxidation, gives 4,5-dehydro-tropone 348, which can be captured (75AG742). 

The tandem cyclopropanation/Cope rearrangement sequence is also applicable to the synthesis of cycloheptatriene derivatives by using dienes with a potential leaving group, e.g., 23f and 23g824. 

Cycloheptatriene derivatives (119) were studied by Seitz and co-workers (Scheme 20) <92CB171>. With electron acceptors R the tricyclic 1,4-dihydropyridazines (120) are obtained which can be oxidized to (121). Donor substituted cycloheptatrienes give the same product in addition to those (122), (123) which result from the addition to the 3,4-double bond of the cycloheptatriene. 

As with other diazoalkanes, diazomethane reacts with alkenes to form cyclopropane derivatives (sec. 13.9.C.i).272 Reaction with aromatic derivatives leads to ring expansion to cycloheptatriene derivatives.223 Both of these reactions (addition to an alkene or arene insertion) involve generation of an intermediate carbene and addition to a jt bond they will be discussed below. Many of the reactions of diazomethane tend to be ionic in nature and are, therefore, set aside from the other diazoalkane chemistry in this section. One of the commonest uses of diazomethane itself is esterification of small quantities of acids, especially acids that are precious for one reason or another. The reaction is quantitative and gives good yields of a single product, as in Tadano s conversion of 338 to the methyl ester of 339224 in a synthesis of (-)-verrucarol. 

Dzhemilev et al. (1991) conducted an interesting investigation on the yield of cycloheptatriene formed in the reaction of benzene with diazomethane with various catalysts. The yield decreases in the presence of transition metal complexes in the series Rh-C (100<7o), Rh2(CF3COO)4 (57q/o), CuCl (39< o), CuBr (37<7o), Rh2(CH3COO)4 (17< o), activated charcoal (15 /o). Toluene, biphenyl, and dimethyl-benzenes yield mixtures of the corresponding regioisomeric cycloheptatriene derivatives in 82-98 yield. With naphthalene, cyclopropanation took place in the 1,2-position only (98< o). The benzonorcaradiene formed resisted isomerization to benzocycloheptatriene. 

In connection with the spiroannelation phenomenon, the final example in this section focuses on the reactivities of bicyclo[6.1.0]nona-triene cation radicals. Spiroannelation at C-9 with a fluorene ring dramatically changes the rearrangement pathway followed in their SET reactions. CA-sensitized photoreaction of 34a gives 1,3,5,7-cy-clononatetraene (38) whereas the DCA-sensitized photoreaction of the diphenyl derivative 34b affords the cycloheptatriene derivative 39 as the sole product. Remarkably, the DCA-sensitized photoreaction of 34c gives the barbaralane derivative 40 as a major product. 

The name tropyliwn and other related names such as tropone CH) and tropolone (HI), which are in normal usage for these cycloheptatriene derivatives, derive from the historic name of cycloheptatriene, namely tropilidine. This in turn comes from tropine (IV), which is a breakdown product of the alkaloid atropine, obtained from deadly nightshade (Atropa belladonna), and from which cycloheptatriene was first prepared, using a series of exhaustive methylation steps [4],... 

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