Enol triflates, transition-metal-catalyzed

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... 

Arylations with aryliodonium salts can be effectively catalyzed by transition metals. The arylation of the lithium enolates of cyclic ketones with di-phenyliodonium triflate in the presence of stoichiometric quantities of copper cyanide affords the corresponding a-phenylated ketones in moderate yields [73]. 

Reactions catalyzed by transition-metal complexes allow the synthesis of a variety of esters ruthenium(II) promotes the addition of acids to alkynes,379 380 e.g. 2,6-difluorobenzoic acid (9) undergoes addition to but-l-en-3-yne to furnish the enol ester 10.380 Aryl bromides381 and aryl or vinyl triflates,382-384 but also aryl chlorides when their tricarbonylchromium(O) complexes are used,385 react with palladium382- 385 or cobalt complexes38 to form a C —M bond. Insertion of carbon monoxide into the carbon-metal bond followed by trapping with an alcohol or phenol leads to ester formation, e.g. triflate 11 gives ester 12.382... 

Ethyl diazoacetate (228 mg, 2.0 mmol) was added at a controlled rate over a 6-8 h period to a stirred mixture of the alkene (20.0 mmol) or diene (10.0 mmol) and the catalyst (0.01 -0,02 mmol) under and ordinarily at 25 C. For copper(I) triflate catalyzed reactions with enol ethers, the diazo ester dissolved in the enol ether w as added to copper(II) triflate in EtjO in order to minimize polymerization of the enol ether. Alkenes were generally purified by distillation prior to their use. The initial solubility of the transition metal compound was dependent on the alkene employed, and, with the exception of Rhg(CO)jg, bis(acetylacetonato)copper(II), and copper bronze, homogeneous solutions were obtained prior to or immediately after the initial addition of ethyl diazoacetate. 1 h after addition was complete, EtjO was added, the resulting solution was washed twice with sat. aq NaHC03 dried (MgSOJ. EtjO and excess alkene were distilled under reduced pressure. The desired cyclopropanes were obtained either by fractional bulb-to-bulb distillation or by preparative GC (Table 8). 

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