Cyclopentenes carbonylation

Simple sugar dehydration/fragmentation products furans, pyrones, cyclopentenes, carbonyl compounds, acids... 

The carbonylation of dehydrolinalyl methyl carbonate (35) at room temperature affords the cyclopentene derivative 37 formed by the ene reaction of... 

Cyclopentene-l-dithiocarboxylic acid, 2-amino-meta complexes, 2, 800 Cyclophane chlorophylls, 3, 58 Cyclophane hemes iron complexes, 4,1269 Cyclophosphazenes metal complexes, 2, 81 Cyclopropane carbonylation... 

C9H(,03 1076-38-6) see Acenocoumarol Ethyl biscoumacetate Tioclomarol Warfarin Zonisamide a-(l-hydroxycyclohexyl)-4-methoxybenzeneacetonitrile (C15H19NO2 93413-76-4) see Venlafaxine (45)-3-[[(lS,2R)-2-hydroxy-3-cyclopenten-l-yl]carbonyl]-... 

This hypothesis is supported by Chauvin s report (33) on a catalyst derived from (CO)5W=C(OEt)C4H9. This highly stable carbene-W(O) compound does not display catalytic activity for cyclopentene monomer. When mixed in the dark with TiCl4, a slow evolution of 1 equivalent of CO occurs. Subsequent thermal or photochemical activation produces ah extremely efficient catalyst system. Chauvin demonstrated that a high conversion to polypentenamer is obtainable at a W/cyclopentene ratio of 10 li at 5°C. The role of TiCI4 is not well understood nevertheless, it promotes carbonyl displacement which appears to be essential. 

Materials. The commercially available aldehydes were distilled prior to use and stored at 0°C under argon. The cyclohexene- and cyclopentene- aldehydes, and the indane aldehyde (see Table) were gifts from Professor E. Piers of this department. The Ru(TPP)(PPh3)2 complex (1) was prepared from Ru(TPP)(CO)(EtOH) and PPh3 (1,7), while Ru(TPP)(CO)(tBu2POH), was prepared from the carbonyl (ethanol) adduct by treatment with tBu2PCl (1). The phosphines were from Strem Chemicals, and the ruthenium was obtained as RuCl Ol O from Johnson, Matthey Limited. 

Using a protocol for tandem carbonylation and cycloisomerization, Mandai et al.83 were able to synthesize cyclopentene and cyclohexene derivatives in high yield, including fused and 5/>/>0-bicycles (Scheme 25). The cyclohexene Alder-ene products were not isolable methanol addition across the exocyclic double bond (in MeOH/ toluene solvent) and olefin migration (in BuOH/toluene solvent) were observed. The mechanism of methanol addition under the mild reaction conditions is unknown. In contrast to many of the other Pd conditions developed for the Alder-ene reaction, Mandai found phosphine ligands essential additionally, bidentate ligands were more effective than triphenylphosphine. 

Volume 75 concludes with six procedures for the preparation of valuable building blocks. The first, 6,7-DIHYDROCYCLOPENTA-l,3-DIOXIN-5(4H)-ONE, serves as an effective /3-keto vinyl cation equivalent when subjected to reductive and alkylative 1,3-carbonyl transpositions. 3-CYCLOPENTENE-l-CARBOXYLIC ACID, the second procedure in this series, is prepared via the reaction of dimethyl malonate and cis-l,4-dichloro-2-butene, followed by hydrolysis and decarboxylation. The use of tetrahaloarenes as diaryne equivalents for the potential construction of molecular belts, collars, and strips is demonstrated with the preparation of anti- and syn-l,4,5,8-TETRAHYDROANTHRACENE 1,4 5,8-DIEPOXIDES. Also of potential interest to the organic materials community is 8,8-DICYANOHEPTAFULVENE, prepared by the condensation of cycloheptatrienylium tetrafluoroborate with bromomalononitrile. The preparation of 2-PHENYL-l-PYRROLINE, an important heterocycle for the synthesis of a variety of alkaloids and pyrroloisoquinoline antidepressants, illustrates the utility of the inexpensive N-vinylpyrrolidin-2-one as an effective 3-aminopropyl carbanion equivalent. The final preparation in Volume 75, cis-4a(S), 8a(R)-PERHYDRO-6(2H)-ISOQUINOLINONES, il lustrates the conversion of quinine via oxidative degradation to meroquinene esters that are subsequently cyclized to N-acylated cis-perhydroisoquinolones and as such represent attractive building blocks now readily available in the pool of chiral substrates. 

Simultaneously to the synthetic studies described above, our model studies had progressed. Although the synthetic challenge in this part of the project was marginal the structure elucidation of the final products was complicated [41]. Starting material for the syntheses was 1-acetyl-1-cyclopentene (58) which was converted into the frans-cyclopentane rac-59 by a Sakurai reaction and a carbonyl olefination (Scheme 16). The synthesis of czs-cyclo-... 

Since the pioneering work by Sarel and co-workers on the iron carbonyl promoted transformation of vinylcyclopropanes and related compounds [1], a variety of transition metal complexes have been examined to achieve effective activation of the vinylcyclopropane-cyclopentene rearrangement which usually requires pyrolytic conditions. These reactions have been applied to natural product synthesis in some cases and have already been reviewed in several excellent articles [2-4]. 

The McMurry reaction (the reductive dimerization of carbonyl compounds giving olefins after treatment with the low-valent titanium reagents TiCla/Mg and TiCla/Zn in THF at 40°C) (CR891513) is a key step in the synthesis of photochromic cyclopentene derivatives. Later, it has been shown that TiCU, which is easier to handle than TiCls, can be used. The cyclization products are formed in 50-60% yields (98S1092,03EJO155). The advantages of this method are that the reactions can be scaled and inexpensive starting materials can be used. 

The meso-ionic l,3-dithiol-4-ones (134) participate - in 1,3-dipolar cycloaddition reactions giving adducts of the general type 136. They show a remarkable degree of reactivity toward simple alkenes including tetramethylethylene, cyclopentene, norbomene, and norbor-nadiene as well as toward the more reactive 1,3-dipolarophilic olefins dimethyl maleate, dimethyl fumarate, methyl cinnamate, diben-zoylethylene, A -phenylmaleimide, and acenaphthylene. Alkynes such as dimethyl acetylenedicarboxylate also add to meso-ionic 1,3-dithiol-4-ones (134), but the intermediate cycloadducts are not isolable they eliminate carbonyl sulfide and yield thiophenes (137) directly. - ... 

The methyl ester has also been obtained by esterification of cyclopentanecarboxylic acid.8 The acid, in turn, has been prepared by the Favorskii rearrangement,6 7 9-11 by the reaction of cyclopentyl Grignard reagent with carbon dioxide,12 by the carbonylation of cyclopentyl alcohol with nickel carbonyl13 or with formic acid in the presence of sulfuric acid,14 and by the hydrogenation of cyclopentene-1-carboxylic acid prepared from ethyl cyclopentanone-2-carboxylate 15 or from cyclopentanone cyanohydrin.16... 

I-N R2 - cyclopentene) 4.5,6.7-TetraOuoro-l. 1,3-triethoxy-carbonyl- E10bz. 115 ( — HF - Cyclopentene-Ringclosure)... 

The most commonly observed dimerization is that of alkenes to form cyclobutane derivatives. Nonconjugated alkenes such as cyclopentene and norbornene are dimerized in the presence of a sensitizer, whereas conjugated alkenes dimerize directly dimerizations of the second type have been observed in dienes, phenyl-ethylenes, and a,/9-unsaturated carbonyl, cyano, and nitro derivatives. The precise structure and stereochemistry of many of these dimers is uncertain, although it is known to be influenced by the solvent, by the presence and nature of substituents, and by the use of a sensitizer. The structures of dimers formed in solid-state irradiations are often determined by crystal structure. 

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