Direct Chlorohydrin and Acetoxy Alcohol Synthesis from Olefins Promoted by a Lewis Acid, Bis(trimethylsilyl) Peroxide and (CH₃)₃SiX

Zirconium(IV)- and Hafnium(IV)-Catalyzed Highly Enantioselective Epoxidation of Homoallylic and Bishomoallylic Alcohols

“…There are many transition metals reported to efficiently catalyze epoxidation of alkenyl alcohols, especially group 4 and 5 metals such as Ti, Zr and V 7. Additionally, as a strong Lewis acid,8 Zr(IV) has been applied in asymmetric epoxidation of homoallylic alcohols 2b,2e. Enlightened by these pioneering work, we therefore chose Ti, Zr, Hf, V and Nb as candidate metal species for our initial experiments.…”

“…These vacant sites could possibly facilitate a slow but significant oligomerization of Zr and Hf species by bridging two or more metals with primary alkoxide anion generated from the substrate or product. Adding DMPU could help the catalyst stay in its monomeric form by occupying these vacant sites on the metals as well as regeneration of the monomeric catalytic species 8b,12. Second, the nucleophilic oxygen of DMPU may help release the coordinated product from the metal and complete the catalytic cycle.…”

Current Methods for Asymmetric Halogenation of Olefins

“…Addition of catalytic (30 mol %) water, which would generate HCl in situ, had a positive effect on the enantioselectivity, increasing the ee values of 70 a and 70 b to 63 % and 66 %, respectively (both in 70 % yield). [43] Scheme 15. [MnA C H T U N G T R E N N U N G (salen)]-catalyzed asymmetric chlorination of olefins.…”

Bis(trimethylsilyl) Peroxide

“…A similar reaction performed in the presence of TMSOAc, albeit with a different catalyst Zr(O i Pr) 4 , resulted in the formation of trans-β-acetoxy alcohols. 32 Chlorohydrins can also be prepared if the corresponding olefins are treated with SnCl 4 and TMSCl in the presence of bis(trimethylsilyl) peroxide. 32 …”