Cyclopentenone synthesis carbonylation

KHAND PAUSON Cyclopentenone Annulat/on Cyclopentenone synthesis from cartxin monoxide acetylene and olefins, cobalt carbonyl catalyzed. 

Interestingly, zirconacyclopentane 246 formed by the reaction of 1,6-heptadiene with the Zr complex has the firms ring junction mainly [108]. It should be noted that the preparation of the trans ring junction in the bicyclo[3.3.0]octane system by other means is difficult. Carbonylation of 246 affords trans-fuzed bicyclo[3.3.0]octanone 247 [109,111]. The diacetoxy compound 248 is obtained by oxidative cleavage of 246. Protonation affords the frans-dimethylcyclopentane skeleton. Similar reactions occur with 1,6-enynes, and Pauson Khand-type cyclopentenone synthesis is possible by carbonylation. 

Cyclopentenone synthesis from carbon monoxide, an acetylene and an olefin catalyzed by cobalt carbonyl or Cp2 n(CO)2 (see 1 st edition). 

Cyclopentenones. The carbonylative stitching method for cyclopentenone synthesis, typified by the Pauson-Khand reaction, includes the variant of using Fe(CO)s under carbon monoxide at relatively high temperatures. 

Pauson-Khand-type reaction." In a cyclopentenone synthesis catalyzed by the titanocene Cp2Ti(PMe.02, trimethylsilyl cyanide supplies the carbonyl unit. 

Allyl complexes have contributed significantly to the development of the organometallic chemistry of nickel and the applications of nickel complexes in organic synthesis, for example, nucleophilic attack on coordinated allyl ligands. In addition, allylnickel complexes have been identified as key intermediates in the oligomerization and cyclization of olefins and dienes. For example, the Ni(0)-catalyzed hydrocyanation of butadiene to adiponitrile, the main component of a major commercial process for the production of nylon, involves Ni (7r-allyl) intermediates. Moreover, the 77-rearrangements of allylnickel species have helped explain the facile isomerization of olefins in the presence of nickel complexes. The Ni-catalyzed homoallylation of carbonyl compounds with 1,3-dienes also involves Ni(7r-allyl) complexes this subject has been reviewed recently. New applications include the cleavage of G-G bonds in the deallylation of malonates, the preparation of cyclopentenones by carbonylative cycloaddi-... 

In a more demanding 1,7-enyne cycloisomerization reaction (36 to give 37), six-membered ring formation using standard conditions proved unfeasible due to the presence of a carbonyl group in the tether and steric hindrance in the alkene moiety. The employment of Pd2 (dba)3 and formic acid, a mandatory acid, allowed smooth cycloisomerization to occur cortpound 37 is an intermediate in the synthesis of (+)-cassiol. Cyclopentenone synthesis is also possible from related 1,6-enynes under similar conditions (eq 23).35... 

Other Octacarbonyidicobalt-Catalyzed Reactions. A retro-Diels-Alder reaction catalyzed by Co2(CO)8 was observed in which a barrelene derivative loses a C2H2 fragment (eq 30). An analogous cleavage accompanies the cyclopentenone synthesis (see below) when norbomadiene reacts in certain solvents with alkynehexacarbonyldicobalts, as shown by the formation of dicarbonylcyclopentadienylcobalt, whereas a Diels-Alder addition catalyzed by a cobalt carbonyl species is involved when the same reaction is applied to cyclohexadiene. ... 

Recent developments have impressively enlarged the scope of Pauson-Khand reactions. Besides the elaboration of strategies for the enantioselective synthesis of cyclopentenones, it is often possible to perform PKR efficiently with a catalytic amount of a late transition metal complex. In general, different transition metal sources, e.g., Co, Rh, Ir, and Ti, can be applied in these reactions. Actual achievements demonstrate the possibility of replacing external carbon monoxide by transfer carbonylations. This procedure will surely encourage synthetic chemists to use the potential of the PKR more often in organic synthesis. However, apart from academic research, industrial applications of this methodology are still awaited. 

Carbonylation of epoxides.4 The epoxide of a 1-alkene undergoes carbony-lation under catalysis with Co2(CO)8 in the presence of K2C03 (1 equiv.) in ethanol at moderate temperatures to afford (3-hydroxy esters. A by-product is the ketone formed by rearrangement of the epoxide. This reaction provides an essential step in the synthesis of the cyclopentenone 3 from the epoxide (1) of ethyl 10-unde-cenoate. 

Moreto and coworkers have made improvements to the Chiusoli reaction, the Ni(CO)4-mediated carbonylation cyclization of allyl halides and alkynes, by conducting it in methanol403. It has subsequently been applied in the synthesis of methylenomycin B, in an intramolecular sense to provide bicyclo[3.3.0]octenones, and in intermolecular cases to form both fused bicyclic cyclopentenones and spirocyclopentenones (equations 203 and 204)403-405. 

Ruthenium complexes are also suitable catalysts for carbonylation reactions of a variety of substrates. Indeed, when a reaction leads to C-Ru or het-eroatom-Ru bond formation in the presence of carbon monoxide, CO insertion can take place at the coordinatively unsaturated ruthenium center, leading to linear ketones or lactones. Thus, ruthenium-catalyzed carbonylative cyclization was involved in the synthesis of cyclopentenones by reaction of allylic carbonates with alkenes in the presence of carbon monoxide [124] (Eq. 93). 

In addition, allenes can act as the olefinic part of the reaction [32], Al-lenynes like 12 may react with both double bonds. Brummond established the substitution patterns for the reaction with either the external or the internal bond of the allenic fragment, that give products with different ring sizes (13— 14) [33]. This group has applied these studies to the synthesis of hydroxy-methylfulvalene (17), a potent anticancer agent related with illudines, a natural sesquiterpene family. The key step was the synthesis of 16 from 15 with a PKR mediated by molybdenum carbonyl (Scheme 6) [34,35]. In addition they have developed an asymmetric version of the reaction. They have transferred efficiently chirality from a non-racemic allene to an a-alkylidene and an a-silylidene cyclopentenone in a molybdenum mediated reaction [36-38]. 

Vinyllithiums of type 663 (R2 = R3 = H) reacted with primary alkyl bromides, carbonyl compounds, carbon dioxide, DMF, silyl chlorides, stannyl chlorides, disulfides and phenylselenyl bromide142,970-979. Scheme 173 shows the synthesis of dihydrojasmone 669 from the corresponding 1,4-diketone. a-(Phenylsulfanyl)vinyllithium 665, prepared from phenyl vinyl thioether, reacted with hexanal and the corresponding adduct 666 was transformed into its acetoacetate. This ester 667 underwent a Carrol reaction to produce the ketone 668, which was transformed into the cyclopentenone 669 by deprotection either... 

Other lithiated vinyl sulfides bearing a carbonyl group at the / -position have been used in organic synthesis mainly as /3-acyl vinyl anion equivalents858. The 2-(isopropylsulfanylmethylene) derivative 673 has been deprotonated with lithium 2,2,6,6-tetramethylpiperidide (LiTMP) to give the intermediate 674 which, after addition to methyl acrylate and final hydrolysis, afforded the cyclopentenone 675 in 70% overall yield981 (Scheme 175). 

The jS-oxycyclopropane carbonyl systems have been used extensively, among other things, for the synthesis of useful 1,4-dicarbonyl compounds, and cyclopentenones derived therefrom. For leading references see M. Julia and M. TchemhoflF, Bull. Soc. Chim. Fr.. 181 and 185 (1956) E. Wenkert, N. F. Golob, R. P. Hatch, D. Wenkert, and R. Pellicciari, Helv. Chim. Acta, 60, I (1977) E. Wenkert, Heterocycles, 44, 1703 (1980) E. Wenkert, R. S. Greenberg, and M. S. Raju, J. Org. Chem., SO, 4681 (1985). 

Allylic halogenides containing an additional internal functional group in a suitable position, e. g., an alkene moiety or a hydroxy group, produce the corresponding cyclopentenone derivatives or lactones, respectively, via palladium-catalyzed carbonylation [43]. Related cyclocarbonylations of cinnamyl halides or acetates to form polycyclic aromatics such as naphthol derivatives have been reported (eq. (15)). Moreover, the synthetic utility of the method was demonstrated by the synthesis of acetoxybenzofurans, acetoxyindoles, and acetoxycarbazoles [44]. 

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