Methyl 3-(Bromomethyl)but-3-enoate and Methyl 3-[(Tributylstannyl)methyl]but-3-enoate in Azomethine Allylation Reactions
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yl 3-(Bromomethyl)but-3-enoate and Methyl 3-[(Tributylstannyl)methyl]but-3-enoate in Azomethine Allylation Reactions D. A. Snetkova and I. V. Mineevaa,* a
Belarusian State University, Minsk, 220030 Belarus *e-mail: [email protected]
Received February 8, 2020; revised April 21, 2020; accepted April 21, 2020
Abstract—Allylation of azomethines was demonstrated for the first time on examples of methyl 3-(bromomethyl)but-3-enoate and methyl 3-[(tributylstannyl)methyl]but-3-enoate. Various systems for the allylation of azomethines under the Barbier reaction conditions were studied and tested. Evidence for the possibility of the addition of allylating agents derived from 3-[(tributylstannyl)methyl]but-3-enoate to azomethines of various structures was obtained. Keywords: methyl 3-(bromomethyl)but-3-enoate, methyl 3-[(tributylstannyl)methyl]but-3-enoate, allylation reaction, azomethine, diastereoselectivity, substituted homoallylamine
DOI: 10.1134/S1070428020080011 Allylation of azomethines is of great interest because it allows one to form a new carbon–carbon bond and extend the carbon backbone, and the resulting homoallylamines are important intermediates in the synthesis of a wide range of products, including biologically active compounds [1]. The high degrees of diastereoselectivity and enantioselectivity in combination with the possibility to prepare allyl derivatives with a broad spectrum of substituents make this allylation reaction a popular approach in organic synthesis [2, 3]. The optically active homoallylamines that form are valuable structural blocks, because they contain not only an asymmetry center but also an allyl fragment, which can be involved in a series of useful modifications via ozonolysis, dihydroxylation, hydrogenolysis, and metathesis [4]. The goal of the present work was to explore the possibility of allylation of azomethines with 3-(bromomethyl)but-3-enoate, a member of the series of 2-substituted functionalized allyl bromides, assess the effect of the structure of the azomethine on the reaction route and stereoselectivity, as well as to find out whether azomethines can take up allylating agents derived from 3-[(tributylstannyl)methyl]but-3-enoate and also whether the allylation reaction products can be used in the design of pharmacophoric fragments.
The allylation of azomethines of various structures with methyl 3-(bromomethyl)but-3-enoate and its related methyl 3-[(tributylstannyl)methyl]but-3-enoate have never been studied and reported in the literature. It should be noted that other 2-substituted functionalized allyl bromides, too, have poorly been studied in azomethine allylation reactions, and the few examples mostly relate to 2-(bromomethyl)acrylates [5–7]. 2-Substituted allyl bromides were prepared by the Kulinkovich reaction and the rearrangement of the corresponding cyclopropanol esters of methanesulfonic acid [8–11]. The results obtained in the present work open up the way to the synthesis of novel biologically active compounds and to a new field of application of 2-substituted f
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