Organic Chemistry Portal

Abstracts

Search:

Highly Selective 1,3-Isomerization of Allylic Alcohols via Rhenium Oxo Catalysis

Christie Morrill and Robert H. Grubbs*

*Arnold and Mabel Beckman Laboratory of Chemical Synthesis, Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, Email: rhgcaltech.edu

C. Morrill, R. H. Grubbs, J. Am. Chem. Soc., 2005, 127, 2842-2843.

DOI: 10.1021/ja044054a


see article for more examples

Abstract

O3ReOSiPh3 promotes the 1,3-isomerization of various allylic alcohols. Two different strategies allow the selective formation of a single isomer. The first strategy utilizes the formation of a conjugated alkene to ensure a high selectivity. The second strategy employs N,O-bis(trimethylsilyl)acetamide (BSA) as an additive to remove the product from the reaction equilibrium and works well for the isomerization of tertiary allylic alcohols.

see article for more examples and reactions



Details

​The document discusses the highly selective 1,3-isomerization of allylic alcohols using rhenium oxo catalyst O3ReOSiPh3 (1). This catalyst, reported by Osborn and co-workers, is highly efficient, achieving equilibrium within 5 minutes at 0 °C. The study explores strategies to enhance selectivity, focusing on substrates with conjugated alkenes and employing low temperatures to suppress side reactions. The reactions are highly E-selective, attributed to steric interactions in the transition state. Electron-rich substrates isomerize efficiently at -50 °C, while electron-poor substrates require temperatures at or above 0 °C. To broaden the scope, the addition of N,O-bis(trimethylsilyl)acetamide (BSA) was found to promote nearly quantitative isomerization of tertiary allylic alcohols to primary alcohols, with the product being selectively silylated to prevent equilibrium. The study also examines the isomerization of enantioenriched allylic alcohols, showing high stereoselectivity with minimal loss of enantiopurity at -78 °C. The findings support a chairlike transition state mechanism and highlight the influence of electronic properties and steric bulk on reactivity and selectivity. The research was supported by the National Institutes of Health and acknowledges contributions from several professors and researchers.


Key Words

Isomerisation of alkenes, allyl alcohols


ID: J48-Y2005-2270