Esters alkynyl

Other pseudo-halides are used for carbonylation. Phenyl tluorosulfonate (484) can be carbonylated to give benzoate[337]. Aryl(aryl)iodonium salts[338], aryl(alkenyl)iodonium salts (485)[339], and arylialkynyl)iodonium salts (486)[340] are reactive compounds and undergo carbonylation under mild conditions (room temperature, 1 atm) to give aryl, alkenyl, and alkynyl esters. lodoxybenzene (487) is carbonylated under mild conditions in... 

Dipolar cycloaddition of 5-aminofuro[3,2-f]pyridinium tosylate 140 and the alkynyl ester 141 yields furo[3,2-f]pyrazolo[l,5- ]pyridine 142 in moderate yield (Equation 33) <1999CCC539>. 

Thus far, the [5 + 2 + 1]-reaction works efficiently with alkynyl esters, amides, aldehydes, and ketones or an alkynyl-substituted allene44 as the two-carbon component (Scheme 58). Just as in the case of the [5 + 21-cycloaddition of VCPs and allenynes, the [5 + 2 + l]-reaction is selective for the allene over the alkyne subunit (Equation (35)). 

Again, the isomerization of an a-alkynyl ester to an allene requires stronger bases, in most known cases sodium amide in liquid ammonia or other strong bases [128, 147-149]. One further example is the step 78 —> 79 from one of the efforts to synthesize myltaylenol [150] (Scheme 1.34). 

Cyclization of secondary alkyl radicals can occur with a, (S-alkynyl esters, such as 12, and proceeds with high stereoselectivity to give predominantly (Z)-exocyclic alkenes at low temperature upon reaction with (TMS)3SiH (Reaction 7.17) [28]. 

It has been demonstrated that Bi(OTf)3 is a versatile catalyst for the activation of both ct- and 7t-donors. Thus, in order to evaluate their potential in terms of a ji-donor/71-acceptor interaction, Bi-catalyzed hydroalkynylations were investigated. As an example, Takaki and coworkers developed a Bi(OTf)3-catalyzed intramolecular carbo-oxycarbonylation of alkynyl esters (Scheme 35) [89]. 

Scheme 36 Possible reaction mechanism for the bismuth-catalyzed carbo-oxycarbonylation of alkynyl esters...

Phosphorus ylides can be generated from triphenylphosphine, 3-chloro-(3//, 5//)-furan-2,4-dione, and alkynyl esters. Additional alkynyl ester, acting as a Michael acceptor, reacts with the ylides in a [4+2] cycloaddition reaction that results in the formation of furo[2,3-3]pyran derivatives (Equation 30) <2000T5221>. 

Alkynyl esters also hydrolyze by this mechanism see Allen Kilamura Roberts Slang Tidwell J. Am. Chem. Soc. 1988, 110. 622. 

RLi (R = 1°, 2°, 3° alkyl aryl vinylic alkynyl ester enolate)... 

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