טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentMaya Preshel Zlatsin
SubjectFormation of Carbon Quaternary Stereogenic Center in Acyclic
systems via a sequence of carbometalation followed
by Intramolecular Cyclization and
Silicon Activation
DepartmentDepartment of Chemistry
Supervisor Full Professor Marek Ilan
Full Thesis textFull thesis text - English Version


Abstract

The highly diastereoselective (dr > 99:1) copper-catalyzed carbomagnesiation reaction of functionalized cyclopropenyl esters was shown to lead to the formation of substituted cyclopropylmagnesium species. Using acylsilanes as electrophiles, α-silyl carbinol species were formed as an intermediate which then underwent intramolecular cyclization. This cyclization leads to the formation of a bicyclic lactone as a single diastereoisomer. Lithium acetylide TMEDA complex reacts with these bicyclic lactones to provide α-pyrones in high yields. Therefore, we hypothesized that the mechanism does not involve reaction of the organolithium on the carbonyl group of the bicyclic lactone as one would expect but rather involved the activation of silicon followed by a Grob - type fragmentation that finally provide the α-pyrone after hydrolysis. α-Pyrone can reacted subsequently with organometallic nucleophiles to give acyclic diketones, hereby showing the potential of the process to be done in a single - pot operation. Indeed, following the use of protic nucleophiles, acyclic carboxylic acids, esters and amides were obtained in a single-pot operation directly from the bicyclic lactones.