to excellent yields with high levels of stereoselectivity. Useful C3-unit elongation, which makes the best use of an allylether as a protecting group and a nucleophilic allylation agent, is demonstrated. Mechanisms for the umpolung reaction (of an allylether into an allylic anion) and stereoselectivity associated with allylation of aldehydes are discussed.
Simple, Facile and Highly Selective Tetrahydropyranylation of Alcohols Using Silica Chloride
作者:N. Ravindranath、C. Ramesh、Biswanath Das
DOI:10.1055/s-2001-18078
日期:——
A simple and efficient process for tetrahydropyranylation of alcohols has been developed by reacting with dihydropyran at room temperature in presence of catalytic amount of silica chloride. The process is highly selective for monoprotection of the hydroxyl groups of symmetric diols.
Efficient and Ecofriendly Protocol for Tetrahydropyranylation/Depyranylation of Alcohols in the Presence of Tin(II) Chloride Dihydrate
作者:Dipankoj Gogoi、Nabajyoti Baruah、Ghanashyam Bez
DOI:10.1080/00397910601055123
日期:2007.3
Abstract A mild, efficient, and solvent‐free protocol for tetrahydropyranylation of alcohols in the presence of a catalytic amount of SnCl2 · 2H2O is reported. Simple filtration of the reaction mixture through a short silica‐gel pad gives the pure products in excellent yields. Depyranylation can also be achieved by adding methanol under similar reaction conditions.
Reaction of alcohols with dihydropyran in the presence of a catalytic amount of Sc(OTf)3 provides efficiently the corresponding tetrahydropyranyl ethers. After the reaction, the catalyst can be recovered quantitatively from the aqueous media and reused without loss of the activity.
Facile Tetrahydropyranylation of Alcohols and Phenols Using Anhydrous Calcium Chloride under Mild and Neutral Conditions
作者:Babasaheb P. Bandgar、Vaibhav S. Sadavarte、Lavkumar S. Uppalla、Suresh V. Patil
DOI:10.1007/s00706-002-0468-9
日期:2003.2.1
Treatment of 3,4-dihydro-2 H -pyran with various alcohols and phenols in the presence of a catalytic amount of anhydrous calcium chloride in dichloromethane furnished tetrahydropyranyl ethers under almost neutral conditions.