Liquid Sulfur Dioxide as a Lewis‐Acidic Solvent for the Alkylation and Alkoxyalkylation of Allylsilanes

Abstract

The ionizing power of liquid SO2 is sufficient to induce reactions between acetals or SN1‐active alkyl chlorides with allylsilanes without additional Lewis acids [Eq. (a), X  OCH3, R  PhCH(OCH3), n‐C6H13CH(OCH3), etc.; X  Cl, R  Ph3C, PhMe2C, etc.]. Reactions in liquid SO2 are economical and ecologically advantageous. An additional benefit: they are extremely simple to perform! equation image

Highly efficient triphenyl(3-sulfopropyl)phosphonium functionalized phosphotungstic acid on silica as a solid acid catalyst for selective mono-allylation of acetals

“…α,β-Unsaturated cinnamaldehyde dimethyl and diethyl acetals smoothly reacted to achieve product yields of 95% and 98%, respectively ( Table 2, entries 15 and 16). The 30PW-Si/TPSP catalyst was also successfully applied to the allylation of o-allylated phenolic acetals showing 93-99% product yield ( Table 2, entries [17][18][19][20][21]. This demonstrates very well the versatility and efficiency of the new catalyst developed for the Hosomi-Sakurai reaction of different functional groups.…”

The remarkable journey of catalysts from stoichiometric to catalytic quantity for allyltrimethylsilane inspired allylation of acetals, ketals, aldehydes and ketones

“…Admiring a high ionizing power of sulfur dioxide (SO 2 ) owing to its electron pair acceptor ability, Mayr et al had used liquid SO 2 as Lewis acid solvent for allylation of acetals. 18 Appreciable factor is recyclability of recondensed SO 2 aer reaction, which avoids aqueous workup. Homoallyl ethers of respective aliphatic and aromatic acetals were produced in good yields ranging from 83-98% by using 1.2 equivalent of allyltrimethylsilane in liquid SO 2 at À60 C. In addition to this, 1,1dimethoxyheptane underwent allylation at 20 C when a tiny crystal of I 2 was added.…”

Allyltrimethylsilane

“…85 The chemoselective allylation of acetals in ionic liquids, such as butylmethylimidazolium hexafluorophosphate and butylmethylimidazolium triflate, is also possible with the use of catalytic TMS triflate. 88 Reaction with Conjugate Enones. 87 Allylation of acetals also proceeds smoothly when using sulfur dioxide as a Lewis acidic solvent.…”