Carbonylation cyclocarbonylation

Unusual cyclocarbonylation of allylic acetates proceeds in the presence of acetic anhydride and an amine to afford acetates of phenol derivatives. The cinnamyl acetate derivative 408 undergoes carbonylation and Friedel-Crafts-type cyclization to form the a-naphthyl acetate 410 under severe condi-tions[263,264]. The reaction proceeds at 140-170 under 50-70 atm of CO in the presence of acetic anhydride and Et N. Addition of acetic anhydride is essential for the cyclization. The key step seems to be the Friedel-Crafts-type cyclization of an acylpalladium complex as shown by 409. When MeOH is added instead of acetic anhydride, /3,7-unsaturated esters such as 388 are... 

Substituted propargylic alcohols were found to undergo direct carbonylation to the corresponding butenolides in 67-98% yield (Eq. 9.120) [86]. This reaction requires a catalytic amount of Pd2(dba)3-CHC13 (4%) and l,4-bis(diphenylphosphi-no)butane (8%) in CH2C12 under an atmosphere of CO (600 psi) and H2 (200 psi) at 95 °C for 36 h. The cyclocarbonylation reaction is believed to proceed via an allenyl-palladium intermediate, which is formed by initial insertion of Pd(0) into the C-O bond of the alkynol followed by rearrangement (Scheme 9.25). 

The Ru-catalyzed cyclocarbonylation of a-allenic sulfonamides proceeds in the presence of Et3N under a CO atmosphere (20 atm) to yield ,/funsaturated lactams (Scheme 16.32) [36], In order to gain an insight into the reaction mechanism, a deuterium-substituted a-allenic sulfonamide was subjected to the carbonylation. The deuterium was found to be totally transferred to the methyl group. Based on this observation, a mechanism has been proposed which involves a ruthenacycle derived from addition of the Ru-H to the terminal double bond of allene (Scheme 16.33). 

All these reactions are examples of oxidative cyclocarbonylation-alkoxy-carbonylation. However, the Pdh/KI catalytic system turned out to be a very efficient catalyst also for promoting cyclization-alkoxycarbonylation processes. In fact, optimal conditions were found for selectively converting 4-yn-l-ols into tetrahydrofuran derivatives (Eq. 41) [107] through 5-exo-dig cyclization followed by alkoxycarbonylation (Scheme 19, path a). This kind of process was not possible for the propynyl, 3-yn-l-ol, and 2-ethynylaniline substrates, seen before, for stereoelectronic reasons [302], With the latter substrates, the endo cyclization mode (Scheme 19, path b), although in principle stereo electronically allowed, was not observed. 

Carbonylation of (diene)ZrCp2 complexes gives cyclopentenones (Scheme 36)51. Since the relative rates of this carbonylation parallel the relative rates for envelope flip of these cr2, n complexes, it might be speculated that initial coordination of CO to the diene complexes (Scheme 36)157. 

Benzodiazocines 182 and 183 were obtained through a sequence of Ugi-depro-tection-carbonylation/intramolecular amidation using ort/io-iodobenzaldehyde and a bifunctional acid or amine [146] (Fig. 36). This cyclocarbonylation was carefully optimized and succeeded in affording 8-membered lactams, which are typically difficult to obtain, in good yields. 

The congeners of 243 and 244 are also formed by the reaction with either Mc2PhSiH or Et2MeSiH (13 silane > 2 1) 243 is readily protodesilylated during purification to give 2,4-diphenylcyclopent-2-enone. When 13 is replaced by 1-hexyne, a product akin to 244 is produced as a major cyclocarbonylation product. At higher temperatures, various types of carbonylation products are produced (Equation (43)). ... 

Cyclobutenes, in Pauson-Khand reaction, 11, 352 Cyclocarbonylation reactions, alkynes, 10, 714 Cyclo-C3 complexes, with molybdenum carbonyls, 5, 440 Cyclo-C4 complexes, in molybdenum carbonyls, 5, 448 Cyclochrome P450cam, aryldiazene reactions, 6, 107 Cyclodextrins... 

Carbonylation of the 3-phenylallyl acetate 258 under somewhat severe conditions in the presence of tertiary amine and acetic anhydride affords the naphthyl acetate derivative 260. This interesting cyclocarbonylation is explained by the Friedel-Crafts-type cyclization of the acylpalladium 259 as an intermediate [118,119]. Even 5-phenyl-2,4-pentadienyl acetate (261) is cyclocarbonylated to afford 2-phenylphenyl acetate (262) [120],... 

Because unsaturated lactones and lactams are of importance as biologically active compounds, the carbonylative cyclization of alkynyl alcohols, alkynyl amines, and their allenyl derivatives has been extensively studied using various transition-metal complexes. Takahashi et al. [35] reported that Ru3(CO)12 also catalyzes the cyclocarbonylation of allenyl alcohols to five- to eight-membered unsaturated lactones (Eq. 20). 

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]. 

Rhodium carbonyl, Rh4(CO)I2, catalyzes the cyclocarbonylation of acetylenes with benzene to give indenones. For example 2,3-diphenyl -indenone is obtained from diphenyl acetylene and benzene in 10% yield, corresponding to a catalytic turnover of 11 (220°C, 25 bar, 7 hr)... 

Another important development in the area of catalytic Pauson-Khand type cy-clizations has been the discovery of other transition metal carbonyl complexes which are capable of effecting the catalytic synthesis of cyclopentenones. Two recent reports from Murai and Mitsudo detailed a Ru3(CO)i2-catalyzed enyne cyclocarbonylation, Eqs. (10) and (11) [34,35]. While this protocol allowed for the cyclization of a variety of l,6-enynes,the cyclizations of terminal alkynes as well as 1,7-enynes were problematic. The feasibility of using Cp2Ti(CO)2 as a catalyst for the intramolecular Pauson-Khand type cyclization of a variety of 1,6-and 1,7-enynes (vide infra) has also been demonstrated [36]. Based on the wide array of transition metals that are capable of effecting stoichiometric Pauson-Khand type cyclizations (vide supra), the development of more catalytic systems is to be expected this should greatly facilitate the search for catalytic asymmetric variants. 

In the course of studying the stoichiometric, carbonylative synthesis of y-buty-rolactones from enones and a titanocene complex [37], it was observed that certain aryl enones could be cyclocarbonylated in a catalytic manner, Eq. (12) [38]. This success in effecting a titanocene-catalyzed cyclocarbonylation led to an examination of the analogous reaction with enyne substrates. Indeed, it was found that under similar conditions, a titanocene-catalyzed Pauson-Khand type cyclization was possible, Eq. (13) [36]. 

Cyclocarbonylation of an a-triazeno-azole in which the terminal nitrogen becomes attached to the carbonyl group is brought about by phosgene, carbonyldi-imidazole or trichloroethyl chloroformate at ambient or lower temperature. Treatment of 2-diazoimidazole (79.9) with isocyanates at — 70°C gives a high yield of the 1,4-cycloaddition product. 

Scheme 57. Heterocyclization of Alkenylamines and Alcohols via (a) Cyclization—/ -Hydride Elimination, (b) Cyclization—/ -Hydroxy Elimination, (c) Cyclization—Acetalization, (d) Cyclocarbonylation, and (e) Cyclization—Carbonylative Esterification...

In a more complicated way, stereospcdfic palladium(II)-catalyzed cyclocarbonylation is achieved with 3-aryl-1-propynes and iodoarenes or acid chlorides, leading to ( >2-arylidenebutenolides S25. This conversion is interpreted as a 1,2-dicarbonylative addition to the corresponding allene. with one of the two newly formed carbonyl groups acting as an ester enolate function. 

Cyclocarbonylation. An intriguing transformation of certain epoxy enynes entails double carbonylation and cycUzation. ... 

Cyclocarbonylation. " When catalyzed by a Rh-carbonyl species and under a CO atmosphere, certain enediynes yield tricyclic ketones. Also involved in this reaction is PhMe,SiH. 

It is interesting that upon illumination, the complex RhCl(CO)(PMc3)2 catalyzes carbonylation of liquified propane at room temperature to yield butanal with high regioselectivity [48], The reaction of some C-H compounds with carbon monoxide and ethylene or other olefins in the presence of metal carbonyls results in carbonylation at a C-H bond [49] (Scheme IV-25). The carbonyl Ru3(CO)i2 catalyzes the cyclocarbonylation of yne-aldehydes to bicyclic a,p-unsaturated y-butyrolactones [49d],... 

Palladium(II) trisulfonated catalysts have been used, with carbon monoxide under pressure and aqueous reaction conditions to carbonylate, for example, 2-hydroxymethyl-5-formylfuran. 5-Methyl-2-formylfuran was obtained in addition to 5-formyl-2-furylacetic acid <94CC2569>. Pal-ladium(O) catalysts have been shown to effect a number of cycloaddition processes that use carbon monoxide as a one carbon component. Benzofurans have been synthesised by cyclocarbonylation <89TL95> and in the example shown in Equation (31) norbomene gave the tricyclic system in good yield <94TL3197> in a reaction where the palladium(O) catalyst was generated in situ. 

This reaction profile, also called carbonylation, governs the reactivity of Pd-carbonyl complexes. Anionic M[Pd(CO)l3], for instance, catalyzes the reductive carbonylation of esters.f On the other hand, Pd(CO)(PPh3)3 was reported to catalyze the carboxymethy-lation of organic halides and the cyclocarbonylation of cinnamyl halides.f " However, the Pd-CO complexes are most often generated in situ from preformed alkyl -palladium complexes and CO under stoichiometric or catalytic conditions, for example, in the copolymerization of alkenes and CO. Decarbonylation reactions also involve the intermediacy of Pd-CO complexes. In this case, migratory deinsertion (Sect, n.3.1), that is, the microscopic reversal of the migratory insertion, takes place. 

In addition to intermolecular carbonylations, there are intramolecular reactions that allow for the synthesis of various heterocycles. As a prime example, the intramolecular alkoxy- or aminocarbonylation (cyclocarbonylation) of hydroxyl-or amino-substituted aryl/vinyl halides enables the synthesis of lactones, lactams, oxazoles, thiazoles, imidazoles, etc. [229]. 

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