Homoallyl esters

Some examples of photolytic intramolecular [2 + 2] cycloadditions which lead to the formation of lactones and lactams are sketched in Scheme 9.9. The allyl ester and N-monosubstituted amide do not undergo cydization, probably because of the high energy of the required E conformers. Cydization of the homoallyl ester does,... 

The basic Markovnikov selectivity pattern is partially or fully overrun in the presence of neighboring coordinating groups within the olefin substrate (Section 2.2.2). Known functionalities where inversed selectivity can occur include 3-alke-noylamides (e.g. 17 reacts to give a mixture of 18 and 19, Table 3) [43], homoallyl esters and alcohols, allyl ethers (but not necessarily allyl alcohols) [44], allyl amines, allyl amides, or carbamates (cf. 20 to 21) [45], allyl sulfides [46] or 1,5-dienes [47]. As a matter of fact, aldehyde by-products are quite normal in Wacker reactions, but tend to be overlooked. 

Both simple and fused poly substituted pyran-2-ones can be obtained from the reaction between substituted allenyl esters and ketones activated by an electron-withdrawing group. A base-catalysed nucleophilic conjugate addition affords a homoallylic ester and lactonisation completes the one-pot sequence (Scheme 19) <06S2731>. 

Solid-supported synthesis has rapidly emerged as an important strategy in synthetic organic chemistry. Solid-phase methodology is aimed at the direct synthesis of libraries of molecularly diverse compounds for biological evaluation in lead discovery. The asymmetric addition of polymer-supported chiral crotylsilanes to acetals and allylation of polymer-bound acetals linked through an ester with the chiral crotylsilanes has been investigated [44d] la can be employed in these crotylation reactions and results in the formation of polymer-supported homoallylic esters with diastereoselec-tivity similar to that of solution-phase reactions. 

A similar change of mechanism is observed in the reaction of silyl-substituted diazo esters 559 with acetaldehyde and benzaldehyde. The Rh2(pfb)4-induced decomposition of allyl ester 559 (n = 1) in the presence of a carbonyl compound yields 1 1 adducts 560, whereas homoallyl ester 559 ( = 2) under the same conditions produces only 1 2 adducts 561 (94CB1537). 

Under the conditions of stoichiometric (eq. (4)) or catalytic (Scheme 2) reactions, propylene is oxidized to isopropenyl acetate as the main reaction product, along with allyl and cis- and trans -n-propenyl acetates. Higher acyclic alkenes C4-C10 are converted to mixtures of allyl and vinyl esters [5]. Cyclic alkenes also produce homoallylic esters [6, 7]. 

Other interesting results pertaiii glycosides, homoallylic esters. 1 participation of an internal hydros... 

Other interesting results pertain to 1,2- and 1,3-asymmetric inductions of C-allyl glycosides, homoallylic esters, and 4-methylene-US-dioxanes. The homologation with participation of an internal hydrosilane leads to cyclic siloxane derivatives. ... 

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