Lewis Acid-Catalyzed Regio- and Stereoselective Allylsilation of Simple Unsaturated Hydrocarbons

Abstract

The reactions of allylsilanes with unsaturated hydrocarbons such as alkenes and alkynes in the presence of Lewis acid catalyst give regio-and stereospecific trans-allylsilylated products in good yields. In the allylsilylations of terminal alkenes and alkynes, the silyl group adds to the terminal carbon and the allyl group adds to the inner carbon of the multiple bonds. Reaction with cyclic olefins gives allylsilylated products having the silyl and allyl groups in trans positions. In allylsilylations with the stereohomogeneous (Z)crotyltrimethylsilane, an allylic inversion is observed indicating a stepwise allylsilylation process. The reaction of conjugated dienes with allylsilanes gives [3+2] annulation products having the silyl and the vinyl groups in trans positions on the ring. Allylsilylation of 5-(trimethylsilyl)-1-pentenes gives unusual allylsilylated products through an intramolecular 1,5-hydride rearrangement reaction in the normal allylsilylated products. All results are consistent with the involvement of silylenium ions in the allylsilylations. 1 Introduction 2 Allylsilylation of Alkenes 2.1 Linear Alkenes 2.2 Cyclic Alkenes 2.3 5-(Trimethylsilyl)-1-pentene 3 Allylsilylation and Intramolecular Cyclization of Diallylsilanes 4 Allylsilylation and [3+2] Cycloaddition of Conjugated Dienes 4.1 Linear Conjugated Dienes 4.2 Cyclic Conjugated Dienes 5 Allylsilylation of Alkynes 5.1 Terminal Alkynes 5.2

An atom-efficient synthetic method: carbosilylations of alkenes, alkynes, and cyclic acetals using Lewis and Brønsted acid catalysts

“…Only one review paper, published in 1999, has focused on allylsilylations. 17 Almost all of the research included in the review consisted of AlCl 3 -catalyzed allylsilylations of alkenes and alkynes.…”

“…In the AlCl 3 -catalyzed reaction, both monoand disilyl cationic species are expected to be catalytically active. 17,18 Formation of a cationic Si species by the reaction between H + sites and allylsilane has been reported. 20,21 The H + site (Brønsted acid site) on the montmorillonite surface can react with an allylsilane to form a cationic Si species.…”

“…co-workers have also reported the PtCl 2 -catalyzed intramolecular arylsilylation (eqn ( 16)). 35 ð16Þ Intramolecular trans-arylsilylation of silicon-tethered alkyne has been demonstrated by Yamamoto and co-workers (eqn (17)). 34 In the case of 4-(dimethylphenyl)silyl-1-butyne, 71% yield of the corresponding five-membered silacycle product (n = 1) was obtained in the presence of a catalytic amount of HfCl 4 .…”

Regio- and Stereoselective Allylindation of Alkynes Using InBr3 and Allylic Silanes: Synthesis, Characterization, and Application of 1,4-Dienylindiums toward Skipped Dienes

“…Allylmagnesations via direct anti -addition of allylic Grignard reagent were also reported ( Scheme 1 A,B), in which a directing group such as hydroxy and amino groups nearby the alkyne moiety are required [ 23 , 24 , 25 , 26 , 27 , 28 , 29 ]. Yamamoto reported an allylsilylation of simple alkynes with allylic silanes catalyzed by either HfCl 4 or EtAlCl 2 -Me 3 SiCl ( Scheme 1 C) [ 16 , 30 , 31 , 32 ]. However, the produced 1,4-dienyl trialkylsilanes cannot be applied to sequential transformations such as Hiyama coupling without activation by a strong base because of their low reactivity.…”

Si-C Coupling Reaction of Hydrosilane with Activated Organic Compounds: A Facile Synthetic Route to Organosilicon Compounds

“…Organosilicon compounds such as allylsilanes [1,2], arylsilanes, vinylsilanes [3], arylfluorosilanes and alkylfluorosilanes [4], and hydrosilanes [5] play an increasingly important role in synthetic organic chemistry [6]. Organosilicon compounds such as allylsilanes [1,2], arylsilanes, vinylsilanes [3], arylfluorosilanes and alkylfluorosilanes [4], and hydrosilanes [5] play an increasingly important role in synthetic organic chemistry [6].…”