Lewis Acid Promoted Mukaiyama Aldol-Prins (MAP) Cyclizations of Acetals, Ketals, α-Acetoxy Ethers, and Orthoformates
作者:Scott Rychnovsky、Michael Gesinski、Lori Van Orden
DOI:10.1055/s-2008-1032053
日期:2008.2
The Mukaiyama aldol-Prins (MAP) cyclization of acetals stereoselectively provided substituted tetrahydropyrans. The scope of the reaction has been expanded to include other electrophiles, including ketals and α-acetoxy ethers. Finally, a double MAP cyclization with orthoformates is described.
A Convenient Method for the Preparation of Secondary Propargylic Ethers. The Reactions of Acetals with 1-Trimethylsilyl-1-alkynes Promoted by the Combined Use of Catalytic Amounts of Tin(IV) Chloride and Zinc Chloride
SnCl4 and ZnCl2, acetals undergo a coupling with 1-trimethylsilylalkynes to give secondary propargylic ethers in good yields. Similarly, propargylic ethers are directly produced from aldehydes by the treatment with alkoxytrimethylsilanes and 1-trimethylsilylalkynes under the same conditions. This catalyst system also efficiently promotes aldol reaction of silylenolethers with acetals or aldehydes, and
A Convenient Method for the Preparation of Secondary Propargylic Ethers. The Reaction of Acetals with 1-Trimethylsilylalkynes Promoted by the Combined Use of Catalytic Amounts of Tin(IV) Chloride and Zinc Chloride
In the coexistence of catalytic amounts of SnCl4 and ZnCl2, acetals undergo a coupling with 1-trimethylsilylalkynes in good yields to give secondary propargylic ethers, which are also directly produced from aldehydes by the reaction with alkoxytrimethylsilanes and 1-trimethylsilylalkynes under the same conditions.
Enantioselective synthesis of crotyl geminal bis(silane) and its usage for asymmetric Sakurai allylation of acetals
作者:Yang Chu、Qiang Pu、Zhixing Tang、Lu Gao、Zhenlei Song
DOI:10.1016/j.tet.2017.05.011
日期:2017.6
Enantioselective synthesis of crotyl geminal bis(silane) 4 has been developed by an asymmetric [1, 5]-hydride shift of allylic hydrazine. SnCl4-promoted Sakurai allylation of (R)-4 with acetals leads to chemoselective desilylation of SiMe3, generating E-syn-(S, R)-5 in good yields with high E/Z-, diastereo- and enantioselectivity.