Allyl rearrangement intermolecular

When there is the intention of effecting an allylic rearrangement in the C—C bond formation step, it is obvious that intramolecular processes are principally better than intermolecular ones as there always exists the competition of 5n versus Ss reactions with intermolecular processes, although there have been a number of improvements regarding this problem in recent years. Because of the huge amount of literature only selected examples, which demonstrate the general trends, can be presented here. 

I.3.I.I.3. Silver(I)-Assisted Rearrangements Intermolecular Quenching of Allylic Cations... 

J.1.1 Intermolecular Reactions with Allylic Rearrangement 4.5.1.J.l Substitution reactions with double bond shift... 

From these results it seems that the epoxy alcohol, IX, does not arise via an intramolecular vanadium-catalyzed rearrangement of cyclohexenyl hydroperoxide, V. An alternative pathway is an intermolecular epoxida-tion reaction between the allylic hydroperoxide, V, and the allylic alcohol which is formed during the oxidation (Reaction 17). We found that IX was produced from reaction of V with VII in the presence of [C5H5V-... 

The-Claisen rearrangement to the ortho position is a first-order reaction,67 68 and the process does not require catalysis by acids and bases. The rearrangement is intramolecular, since rearrangement of mixtures of ethers such as allyl /3-naphthyl ether and cinnamyl phenyl ether,60 or cinnamyl 4-methylphenyl ether and allyl 4-aminophenyl ether,68 yields none of the cross products which would result from an intermolecular reaction. The process is best represented by the cyclic mechanism, in which the following processes take place, with the electronic shifts during reaction indicated by the arrows.23 39 69... 

The thermal rearrangement of allyl ethers is a process entirely different from. the rearrangement of saturated alkyl phenyl ethers by acidic catalysts.103 The latter process seems to be intermolecular, gives consider-... 

Perhaps the seminal work on the subject of this review is that of Balavoine and Guibe. They studied the Pt(0)-catalyzed (not Pd) isomerization of 2-allyloxypyridine 138 (Scheme 29) into N-allyl-2-pyridone 139 (N > O) (79TL3949). The intermolecular nature of the rearrangement, through a common Tj3-allylplatinum intermediate, is indicated by the transformations of both ethers 140 and 141 into the same mixture of A -allylated isomers 142 and 143. 

The ruthenium-catalysed direct addition of saturated aliphatic alcohols to non-activated alkynes remains a challenge. Only allyl alcohol has been successfully involved in the intermolecular addition to phenylacetylene to produce an ether and the enal resulting from Claisen rearrangement (Scheme 7) [22]. Thus, in refluxing toluene, in the presence of a catalytic amount of RuCl(tris(pyra-... 

The reaction of oxetane with carbenes follows two major pathways carbonhydrogen insertion or the formation of an oxygen ylide by reaction of the carbene and the oxetane oxygen. The oxygen ylide can produce a tetrahydrofuran by a Wittig rearrangement or generate an allyl ether by an intermolecular -elimination process (Scheme 61). 

Although the addition of methanol to electron-deficient alkynes such as acetylene dicarboxylates is easy, the intermolecular addition of alcohol to unactivated alkynes in the presence of ruthenium catalysts to form enol ethers is not straightforward, and the only reported examples concern the addition of allylic alcohols to terminal alkynes. Thus, in the presence of a catalytic amount of RuCl(tris(pyrazolyl)borate)-(pyridine)2, allyl alcohol adds to phenylacetylene in refluxing toluene to produce a 1 1 mixture of allyl /3-styryl ether and 2-phenylpent-4-enal (resulting from Claisen rearrangement) (Scheme 8.7) [17]. 

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