Abstract

A. BRAVO, José  and  L. VILA, José. Synthesis of alkenes: claisen rearrangement of allyl vinyl ethers, part ii; mechanistic views; the organic chemistry notebook series, a didactical approach, nº 10. Rev. Bol. Quim [online]. 2016, vol.33, n.2, pp.95-103. ISSN 0250-5460.

This is the tenth theoretical assay in the series: "The Organic Chemistry Notebook Series, a Didactical Approach". The aim of this series of studies is to help students to have a graphical view of organic synthesis reactions of diverse nature. We have taken a series of reactions compiled by W. Carruthers in 'Some modern methods of organic synthesis', and we have proposed didactical and mechanistic views for them. This theme is included in the chapter "Formation of carbon-carbon double bonds" in the mentioned text. In the present chapter, we expose a complementing of Claisen rearrangements of ally-vinyl ethers. A first approach in this study comports the Claisen rearrangement feature regarding the stereochemical control that conducts to the definition of the positioning of substituents on the new single bond that arises from rearrangement. This feature serves as a sort of transmission of chirality along a carbon chain. We proposed mechanisms for this feature. As an example we elaborated mechanisms for a key step in the synthesis of (+)-15(S)-prostaglandin A2 involving the stereochemical control mentioned. We also covered from a mechanistic stand point the theme of the geometry of the enol ether double bond and its control by means of the procedure described by Ireland. We elaborated too, the mechanisms for the conversion of allylic ester into the E-ketene acetal or the Z-ketene acetal and subsequent acid formation including the example of the E-crotyl propanoate and the Z-crotyl propanoate.

Keywords : Organic Chemistry; Alkenes; Allyl vinyl ethers; Claisen rearrangement; Mechanisms of Reactions; W. Carruthers.

        · abstract in Spanish     · text in Spanish     · Spanish ( pdf )