Cycloisomerizations allyl propargyl ethers

Cycloisomerization of allyl propargyl ethers takes place under mild conditions when performed with a ruthenium hydride catalyst obtained from Cp RuCl(COD) in the presence of acetic acid or ethanol. 3,4-Dialkylidenete-trahydrofurans were produced in good yields [ 71 ] (Eq. 53). It is noteworthy that the C-H and C-C bonds formed are always syn. This is the result of the cis addition of the Ru-H bond to the C=C bond. 

Platinum(ll)-catalyzed carbocyclization of a.ty-enynes has been intensively researched lately. For instance, 2-disubstituted l-en-6-ynes react with methanol in the presence of PtCl2 as catalyst to form carbocycles with exocyclic aUcenes. The analogous reactions of 3-allyl propargyl ether or 3-allyl propargyl tosylamine in water using the same catalysts will generate cyclopropyl aldehydes besides the product of cycloisomerization (Scheme 82). The coordination of the... 

General procedure for the enantioselective gold-catalyzed cycloisomerization of allyl propargyl ether ... 

The catalysts precursors A and B contain no Ru carbene at the outset of the reaction. Thus, the question arises whether the cycloisomerization of the allyl propargyl ethers reported above proceeds via a metathesis pathway or another type of mechanism (see Section 2). To try to answer this question, a catalytic transformation of dienes was attempted with the catalytic system B, A complete conversion of the starting dienes into the cycloisomerization methylenecycloalkane derivatives 71-74, isolated in 64-88%, was observed... 

The high-valent metal species required for activation of an alkyne has also been generated by the oxidative addition to an allylic or propargylic system. For example, with an allyl aryl ether as the substrate, this type of reaction achieves a cycloisomerization that occurs through an 0- to C-allyl migration (Equation (92)) 323,324 similarly, (9-propargyl derivatives lead to a mixture of allenyl and propargyl products (Equation (93)).325,326... 

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