Cycloadditions of Allylsilanes - Part 22.¹ Stereoselective Synthesis of Cyclopentanes and Cyclobutanes by Lewis Acid Promoted [3+2] and [2+2] Cycloadditions of Allylsilanes

Propargyl silanes with a terminal alkyne moiety undergo a 1,2-silyl shift when activated with electrophiles such as H+, Br+, I+, and PhSe+. A method was developed to trap 1,3-transposed electrophilic centers with various internal O-, N-, and S-nucleophiles in a 5-exo manner. This synthetic procedure provided five-membered heterocycles containing a trisubstituted olefin side chain. The scope of the method includes access to tetrahydrofuran, γ-butyrolactone, 2-isooxazoline, pyrrolidine, and thiolane derivatives in yields ranging from 25 to 85% (23 examples in total). Reactions with TsNBr2 ensured complete (E)-selectivity of the newly formed olefins. Further functionalization of the obtained 1-trialkylsilyl-2-bromovinyl side chain was demonstrated by double-bond geometry-preserving electrophilic substitution and cross-coupling reactions that provided heterocycles with a trisubstituted vinyl moiety.

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1,3-Difunctionalization of Propargyl Silanes with Concomitant 1,2-Silyl Shift: Synthesis of Allyl Functionalized Vinyl Silanes

Beļaunieks,

Puriņš,

Līpiņa

et al. 2023

Org. Lett.

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Terminal alkynes with a silyl group at the propargylic position upon activation with electrophiles such as N-bromosuccinimide undergo (E)-selective 1,2-silyl group migration. Subsequently, an allyl cation is formed that is intercepted by an external nucleophile. This approach provides allyl ethers and esters with stereochemically defined vinyl halide and silane handles for further functionalization. The scope of propargyl silanes and electrophile–nucleophile pairs are investigated, and various trisubstituted olefins are prepared in up to 78% yield. The obtained products have been demonstrated to serve as building blocks for transition-metal-catalyzed cross-couplings of vinyl halides, silicon-halogen exchange, and allyl acetate functionalization reactions.

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Cycloadditions of Allylsilanes - Part 22.¹ Stereoselective Synthesis of Cyclopentanes and Cyclobutanes by Lewis Acid Promoted [3+2] and [2+2] Cycloadditions of Allylsilanes

Cited by 6 publications

References 92 publications

Formation of Alkanes and Arenes by Ring‐forming Reactions

Formation of Alkanes and Arenes by Ring‐forming Reactions

1,2-Silyl Shift-Induced Heterocyclization of Propargyl Silanes: Synthesis of Five-Membered Heterocycles Containing a Functionalized Olefin Side Chain

1,3-Difunctionalization of Propargyl Silanes with Concomitant 1,2-Silyl Shift: Synthesis of Allyl Functionalized Vinyl Silanes

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