Conia-ene-reaction

In this reaction, silver is successful (Table 12.11, entry 1) gold(III) leads to an unselective conversion (entry 2), but gold is more active and selective. As usual, coordinatively saturated gold complexes fail (entry 3), but cationic gold complexes deliver very good yields in short reaction times (entries 4 and 5). 

In a recent (2009) publication, Jin-Heng Li reported a copper/silver-cocatalyzed version of this isomerization.30 With the same substrate, here the combination of copper and silver is able to compete with the gold catalysts (entries 6 and 7). 

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Claisen or Cope rearrangement Ester cracking Conia ene reaction... 

The Conia-ene reaction is a thermal cyclization of an alkyl ketone with an alkyne to give the corresponding a-vinylated ketone.98 The catalytic version of this reaction has been reported to generalize the process to more functionalized substrates.99 The intramolecular carbocupration of alkyne 94 has been investigated under basic conditions in the presence of a catalytic amount of copper iodide (Scheme 28).100 The cyclic product 95 is obtained in high yield. 

The phyllocladane skeleton 131 was constructed efficiently by stereoselective formations of six carbon-carbon bonds and four rings via a one-pot sequence of cyclizations the ene type, [2+2+2], and [4+2] cycloadditions. In this synthesis, the Conia ene reaction of 127 takes place under mild conditions to generate 128, and the cyclotrimerization of its diyne with 118 gives 129. These two reactions are catalysed by CpCo(CO)2. Finally, ring-opening to give 130 and intramolecular Diels-Alder reaction in the presence of DPPE produced the phyllocladane skeleton 131 in a total yield of 42% [55]. 

The Conia-ene reaction was brought to the held of gold catalysis by Toste et al.29 It provided very mild conditions for this cyclization to a functionalized hve-membered ring (Scheme 12.14). 

Another version of the Conia-ene reaction is the focus of this research. Here the reaction of y-alkynic (3-ketoesters was tested.48 The screening resulted in a copper / silver cocatalysis system. It remains unclear why the authors did not at least run some reactions with gold catalysts, too, especially since they even cite the work on the gold-catalyzed Conia-ene reaction in the introduction (Section 12.1). 

The thermal cyclization of ketones onto alkynes, the Conia-ene reaction, can proceed thermally but only at inconveniently high temperatures.39 Transition metals can catalyse it at lower temperatures but they require enolate generation, strong acid or photochemical activation. In the presence of phosphaneAu1 complexes, however, the reaction proceeds at ambient temperature under neutral conditions. For example, the following ketoester was converted into the cyclic product in 94% yield in 15 min in the... 

Enophiles may include carbonyls, thiocarbonyls, imines, alkenes and alkynes. When the carbonyl is an enophile, the reaction is called a carbonyl ene reaction. The enol form of an unsaturated ketone may serve as an ene in an intermolecular ene reaction known as the Conia-ene reaction. Ene reactions proceed best when the enophilic double bond is electron deficient. Hydrogen is the most common atom transferred in an ene reaction. Other atoms or groups may, however, participate in ene-like transformations. 

In the Conia-ene reaction, a carbonyl compound enolizes and then undergoes an intramolecular ene reaction. The enol fragment serves as the ene component of the reaction, while the olefin fragment serves as the enophile. An example is the reaction of 8-methyl-7-nonen-2-one (92), which yields 2-isopropylcyclopentyl methyl ketone (93, equation 11.41). ... 

The Conia-ene reaction of P-ketoesters bearing a pendant triple bond involves the cycloisomerization of an enyne formed by enolization. This transformation is efficiently catalyzed by cationic gold(I) complexes and afforded cyclopentane derivatives with excellent yields and moderate to good diastereoselectivities (Scheme 4-40). Acetylenic silyl enol ethers or imines react in an analogous manner. By this method, iodoalkynes were converted into iodocyclopentenes, which are highly useful in natural product synthesis. 

The Conia-Ene reaction is an intramolecular ene reaction of unsaturated ketones, in which the carbonyl functionality serves as the ene component, via its tautomer, and olefinic moiety serves as the enophile. Some of the important examples are summarized in Scheme 6.13. 

Conia-ene reactions [24], respectively (Scheme 26.3a and b), while DBU has been used to generate enamines for palladium-mediated allylation with allylic carbamates [25] (Scheme 26.3c). More recently, Shibasaki s group studied the cooperation of Cu(CH3CN) (soft Lewis acid) and Li(OC5H4-p-OMe) (hard Brpnsted base) in the conjugate addition of terminal alkynes... 

When an unsaturated ketone in enol form undergoes ene reaction, the reaction is known as the Conia ene reaction [3]. The following examples [3-5] are illustrative. 

Yang T, Ferrali A, Sladojevich F, Campbell L, Dixon DJ (2009) Bronsted base/lewis acid cooperative catalysis in the enantioselective conia-ene reaction. J Am Chem Soc 131 (26) 9140-9141... 

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