Carbonylation aryl/enol triflates

Carbonylation of enol triflates derived from ketones and aldehydes affords Q,/)-unsaturated esters[332]. Steroidal esters are produced via their aryl and enol triflates[328]. The enol triflate in 477 is more reactive than the aryl tritlate and the carbonylation proceeds stepwise. First, carbonylation of the enol triflate affords the amide 478 and then the ester 479 is obtained in DMSO using dppp[333]. 

Triflates derived from phenols are carbonylated to form aromatic esters by using Pd-Ph3P. The carbonylation of triflates is 500 times faster if DPPP (XLIV) is used [219]. This reaction is a good preparative method of benzoates from phenols and naphthoates from naphthols [220]. Carbonylation of enol triflates derived from ketones and aldehydes affords a,/Cunsaturated esters. The enol triflate in 451 is more reactive than the aryl triflate and the carbonylation proceeds stepwise chemoselectively. At... 

The most useful pseudo-halides are aryl triflates (trifluoromethylsulfonates) of phenols and enol triflates derived from carbonyl compounds[4,5,6]. 

Carboxylic acids are produced in water. Selection of solvents is crucial and the carbonylation of the enol triflate 480 can be carried out in aqueous DMF, and that of the aryl triflate 481 in aqueous DMSO using dppf as a ligand[328,334]. The carbonylation of the enol triflate 482 to form the a, 0. unsaturated acid 483 using dppf as a ligand in aqueous DMF has been applied in the total synthesis of multifunctionalized glycinueclepin[335]. 

The carbonylation of o-diiodobenzene with a primary amine affords the phthalimide 501 [355,356], Carbonylation of iodobenzene in the presence of odiaminobenzene (502) and DBU or 2,6-lutidine affords 2-phenylbenzimida-zole (503)[357], The carbonylation of aryl iodides in the presence of pentafluor-oaniline affords 2-arylbenzoxazoles directly. 2-Arylbenzoxazole is prepared indirectly by the carbonylation of n-aminophenol[358]. The optically active aryl or alkenyl oxazolinc 505 is prepared by the carbonylation of the aryl or enol triflates in the presence of the opticaly active amino alcohol 504, followed by treatment with thionyl chloride[359]. 

The conversion of carbonyl compounds to their enol triflates provides a very simple way to couple the carbonyl carbon to an alkene. In general, however, aryl... 

Meyers and colleagues described the palladium-catalyzed carbonylative synthesis of oxazolines as early as 1992 [268]. Aryl or enol triflates made from the corresponding ketones and phenols, and also aryl halides, were used as starting materials and coupled with amino alcohols to give chiral a,)S-unsaturated or aryl oxazolines in good yields. Later on, Perry s group performed systematic studies on this one-pot, two-step process for the preparation of oxazolines (Scheme 2.37) [269, 270]. 

These results indicate that we can introduce various substituents onto the carbonyl carbon using a palladium catalyst. Thus, aryl triflates were converted into aryl esters or amides (Scheme 17, Table 6), and enol triflates could be converted into a,/3-unsatu-rated esters or amides by a Pd-catalyzed reaction with carbon monoxide and alcohols or amines (Eq. 

Since the discovery of Pd-catalyzed carbonylation of aryl, vinyl, and benzyl halides by Heck in 1974, this reaction has been used for the synthesis of ester, amide, acid, and acid anhydride. We can nse enol triflate, aryl Iriflate, aniUne derivatives, and vinyl silane as the pseudo aryl or vinyl halide. This reaction has now been further extended for the synthesis of aldehyde and ketone by combination with transmetalation. These reactions have widely been used in organic syntheses, especially the syntheses of biologically active substances in the field of fine chemistry and the syntheses of natural products. 

Chiral Q , -unsaturated oxazolines can be obtained by a carbonylation-amidation of enol triflates or aryl halides with chiral amino alcohols (eq 36). The palladium catalyst can be either Pd(PPh3)4, bis(dibenzylideneacetone)palladium(0) and PPh3, or Pd(OAc)2 and dppp in the presence of triethylamine. 

Deoxygenation of Carbonyls. Carbonyl compounds can be deoxygenated to form alkenes in a palladium-catalyzed reduction of enol triflates (eq 72). The reaction is quite general, and has been applied to aryl as well as alkyl enol triflates. ... 

On the other hand, the use of [Rh(CO)2Cl]2 as a catalyst results in ring opening of the siloxycyclopropanes 13 to the silyl enol ethers 14 with high stereoselectivity [10]. The 2-siloxyrhodacyclobutane 15a is proposed to undergo j8-elimination to give jr-allylrhodium 16a followed by reductive elimination to the silyl enol ether 14a. 1-Trimethylsiloxybicyclo[n.l.0]alkanes serve as / -metallo-carbonyl compounds via desilylation with a variety of transition metals [11]. The palladium-catalyzed reaction of the siloxycyclopropanes 17 under carbon monoxide in chloroform provides a route to the 4-keto pimelates 18. In the presence of aryl triflates, the 1,4-dicarbonyl compounds 19 are... 

Reaction of diphenylsulfoxide with triflic anhydride affords, as precedently mentioned, the corresponding sulfoxonium triflate, a powerful reagent for numerous reactions, such as a-arylation of carbonyls, enolate additions,or nucleophilic substitution on alkenes (102). ... 

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