Synthesis of functionalized γ-lactone via Sakurai exo -cyclization/rearrangement of 3,3-bis(silyl) enol ester with a tethered acetal
An efficient synthesis of functionalized γ-lactones has been developed involving Sakurai exo-cyclization/rearrangement of 3,3-bis(silyl) enol esters with a tethered acetal. While the steric and electronic effects of geminal bis(silane) favor the desired Sakurai pathway, the methoxy species formed in the deprotection step also facilitates both cyclization and rearrangement. The synthetic value of this approach has been demonstrated by efficiently transforming the E-vinylsilane into enyne and the γ-lactone moiety into multisubstituted THF.
Facile Synthesis of Some Substituted Methyl 3-Formylpropanoates
Variously substituted methyl 3-formylpropanoates are prepared in high yields by the reaction of methyl 4,4-dimethoxybutanoates with titanium tetrachloride.
Concurrent Anodic Cyanation and Methoxylation of Methylated Furans. Oxidation Potential and Reactivity, and Stereochemical Control of Addition
The potentiostatic electrooxidation of a series of methyl-substituted furans was performed in MeOH that contains NaCN at a Pt anode in a divided cell.In all instances, the 1,4-additions of cyano and/or methoxyl group(s) across the furan ring were achieved.Replacement of an aromatic hydrogen by a cyano group occured concurrently in some cases.The relative rates of cation radicals toward two different nucleophiles (CN- ion and the solvent MeOH) (or the MeO- ion as a result of the equilibrium between CN- ion and the solvent MeOH) at the electrode surface were determined from the yields of products by using the rate expressions of competitive reactions.There is a linear correlation between the relative reactivity of the furans (on a log scale) and their oxidation potential.The ratio of stereoisomers formed in an electrooxidation of 2,5-dimethylfuran (2,5-DMF) changes with addition of adsorbable compound as well as substrate concentration and this is thought to be due to the influence of concentration (or coadsorbate) on substrate orientation in the adsorption layer.
Yoshida, Kunihisa,Fueno, Takayuki
p. 229 - 240
(2007/10/02)
Convenient Syntheses of 4,4-Dimethoxy Esters and Ketones