Diastereoselective Synthesis of Seven-Membered-Ring trans-Alkenes from Dienes and Aldehydes by Silylene Transfer

Abstract

Silver-catalyzed silylene transfer to alkenes formed vinylsilacyclopropanes regioselectively. These allylic silanes underwent additions to aldehydes to form seven-membered ring trans-alkenes with high diastereoselectivity. The high reactivity of the trans alkenes is evidenced by their formal [1,3]-sigmatropic rearrangement reactions and their rapid additions of oxygen–hydrogen bonds across the carbon–carbon double bonds.

High Reactivity of Strained Seven‐Membered‐Ring trans‐Alkenes

“…[2] Among the strained systems investigated, the eight-membered-ring trans-alkenes have found numerous applications. [12][13][14] They also participate in reactions observed for trans-cyclooctenes,s uch as [4+ +2] cycloadditions, [3,10] but those reactions were generally low-yielding.Herein, we demonstrate that highly strained trans-oxasilacycloheptenes undergo fast, high-yielding,a nd, in most cases,s tereoselective reactions.T hese strained alkenes are more reactive in a[4+ +2] cycloaddition than the most reactive trans-cyclooctene. [9][10][11] Limited studies of the chemistry of trans-cycloheptenes demonstrate that they undergo transformations typical of reactions of alkenes,s uch as dihydroxylations [11,12] and reactions with acids.…”

“…[9][10][11] Limited studies of the chemistry of trans-cycloheptenes demonstrate that they undergo transformations typical of reactions of alkenes,s uch as dihydroxylations [11,12] and reactions with acids. This sevenmembered-ring trans-alkene,w hich was synthesized from 1,3-pentadiene,b enzaldehyde,a nd ad i-tert-butyl silylene source, [14] reacted with diene 2 within five minutes (Scheme 1). [15,16] Thet unable synthesis of these sevenmembered-ring trans-alkenes allows access to new strainpromoted reactions,i ncluding stereoselective reactions with substrates containing electron-deficient p-bonds.…”

“…This sevenmembered-ring trans-alkene,w hich was synthesized from 1,3-pentadiene,b enzaldehyde,a nd ad i-tert-butyl silylene source, [14] reacted with diene 2 within five minutes (Scheme 1). This sevenmembered-ring trans-alkene,w hich was synthesized from 1,3-pentadiene,b enzaldehyde,a nd ad i-tert-butyl silylene source, [14] reacted with diene 2 within five minutes (Scheme 1).…”

“…Them odular assembly of seven-membered-ring transalkenes from dienes and aldehydes by silylene transfer [14] enables the synthesis of other electron-rich trans-cycloalkenes.Strained silyl enol ether 12,the first example of asilyl enol ether incorporated into a trans-cycloalkene,w as even more reactive with quinones. [27] Upon exposure to quinone 10 a or 10 b,phenols 13 a and 13 b,respectively,were formed as single stereoisomers [Eq.…”

[4+2] Cycloadditions of Seven‐Membered‐Ring trans‐Alkenes: Decreasing Reactivity with Increasing Substitution of the Seven‐Membered Ring

“…Silver‐catalyzed silylene transfer to 1,3‐diene 9 afforded vinylsilacyclopropane 11 in 80 % yield. Addition of benzaldehyde to vinylsilacyclopropane 11 yielded trans ‐oxasilacycloheptene 12 in 99 % yield , . trans ‐Alkene 12 was unstable to atmospheric conditions and it underwent thermal rearrangement .…”