Cycloheptene-based

Ni-catalysed rearrangement of cyclopropylenynes gives cyclopentane- and cycloheptene-based heterocycles (Scheme 80).122... 

Bacque et al. have reported new approaches to cycloheptenes based on pathway a [86]. 

Several isomerization reactions have been reported by Louie and coworkers. In 2004, the isomerization of a variety of vinyl cyclopropanes to afford cyclopen-tenes was reported (Figure 13.41) [90]. When an appended alkyne was added to the vinyl cyclopropane, a variety of substituted cyclopentane- and cycloheptene-based heterocycles could be synthesized [91]. Vinyl aziridines and aziridinyle-nynes could also be used in a similar system to synthesize either imines or a variety of heterocyclic products, respectively [92]. Finally, during development of cycloaddition reactions, an interesting isomerization product was observed from enyne isomerization to yield a diene [93]. 

Using substituted a-methylene-(3-acetoxy ketones 2-494 with R = Me, Et, iPr, Ph and LiOtBu as base, the yields of the cycloheptene oxide 2-498 could be greatly enhanced to up to 77 %, as in the case of2-498b. In addition, cyclooctene oxides can be prepared (though in lower yield and stereoselectivity) starting from a six-membered oxosulfonium ylide. 

Trost and Toste51 isolated unexpected cycloheptene 69 upon exposing enyne 68 to their optimized ruthenium-based Alder-ene conditions (Equation (42)). Further exploration into the effects of quaternary substitution at the propargylic carbon revealed the ability of ruthenium to catalyze a non-Alder-ene cycloisomerization to form seven-membered rings, presumably via allylic C-H activation (Scheme 15). 

An extensive study of the conformational behavior of perhydroazepine 66 was carried out by Espinosa and coworkers105. This pure force field based analysis, with no reference to experiment or other theoretical methods, was part of a series of studies on cycloheptane, cycloheptene and some of their oxygen, sulfur and nitrogen heterocyclic analogs. MM2... 

Two suggested methods of nortriptyline synthesis are based on the N-demethylation of amitriptyline. The third way utilizes the reaction of methylamine with 5-(3-bromopropyli-den)-10,11 -dihydro-57f-dibenz [a,d]cycloheptene (7.1.18). 

The results are based on variable-temperature (VT) H NMR studies of 23-31. The results are close to those found for 2-aminoacetophenone, AG = 10.5 0.5 kcalmol-180. In addition, for the four compounds 25-28 characterized by the cycloheptene moiety, a slow ring interconversion from chair to chair was evident. For compounds 25, 27 and 28 the experimental AG values were 9.4, 10.2 and 10.0 kcalmol-1, and the corresponding coalescence temperatures were 204, 220 and 215 K, respectively. For compound 26 these values are not available. 

In fact, reactivity of 1-chloro cycloheptene looks like reactivity of 1-chloro cyclohexene95,103,10S and reactions with nucleophilic complex base NaNH2-enolates lead to compounds similar to the ones isolated in cyclohexenic series. This is exemplified in Scheme 65 with alicyclic ketone enolates. 

Silver(I) triflate performs several functions 1. it catalyzes the deamination of nitrosourea 20 and renders a base unnecessary 2. it stabilizes the trani-cycloheptene derivative by complexa-tion 3. it probably catalyzes the [4 + 2] cycloaddition by precoordination of the diene. 

Based on MM2 results, predictions have been made for the structure of frans-cyclohexene (43a) and frans-cycloheptene (39a). rrans-Cyclohexene... 

Isomerization of epoxides to allyiic alcohols. This reaction is usually carried out with base (lithium diethylamide, 1, 610-611 2, 247-248 4, 298). Japanese chemists have used instead this new reagent of the type R R NAl(C2Hs)2, which is effective because of the affinity of aluminum for oxygen. Of several species, DATMP proved most satisfactory. It effects the isomerization of (1) and of (3) in high yield under very mild conditions. Note, however, that the oxides of cyclopentene, cyclohexene, and cycloheptene are stable under the same conditions. 

There have been several reports of the use of ring-closing metathesis applied to sugar-derived compounds for the preparation of cycloheptene and cyclooctene derivatives. The mannose-derived dienes 42 (R = H, Ac) were converted in high yields to the carbocycles 43 using Grubbs ruthenium-based catalyst, and the... 

LiHMDS, the qrcloheptene oxide derivative 42 was obtained in lower yield (23%), whereas with substituted 41 and liOt-Bu as base, yields of 42 could be greatly enhanced up to 77% (R =i-Pr, R = Ph) [23b]. The cycloheptene oxides 42 are considered to be formed through Sj 2 substitution of yUde 40 on 41 and subsequent intramolecular Corey-Chaykovsky reaction of the resulting ylide 44 through intermediate 45 (Scheme 4.9). 

Cyclic alkenes are known compounds. As with cyclic alkanes, the parent name for cyclic alkenes is based on the number of carbon atoms in the ring derived from the analogous linear alkene, but the prefix cyclo is added to the name. The six-carbon cyclic molecule that contains a C=C unit is called cyclohexene (4). Substituents are named in the usual manner, and one carbon of the C=C unit must be Cl. The choice of which C=C carbon becomes Cl is dictated by giving the substituents the lowest number. Compound 5 is a cycloheptene, but the substituents can be numbered 6-ethyl-3,6-dimethyl- or 4-ethyl-4,7-di-methyl. The smaller numbers dictates the priority, which also give the ethyl group the lower number, and 5 is 4-ethyl-4,7-dimethylcycloheptene. Note that the 1-heptene is unnecessary in the name... 

The deprotonation of epoxides was reported twice. A 4-substituted cycloheptene oxide (95) was deprotonated with an organolithium base in the presence of a chiral... 

Cyclopentene was reported to copolymerize with cycloheptene in the presence of WClg- or WOCI4-based catalysts [35], yielding copolymers with structure (55), having a high trans content of the double bonds in the chain ... 

Carbocations adjacent to cobalt-alkyne complexes that are also conjugated to tt bonds enable a variety of conjugate addition options. Sierra and de la Torre reported examples for the synthesis of terpene-based hybrids. Treatment of alcohol 19 with boron trifluoride and furan furnished addition product 20 via an SnI mechanism. Green employed a similar strategy for the synthesis of substituted cycloheptenes. ... 

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