Stereoselectivity in the Wittig reaction depends on the ylid
المؤلف:
Jonathan Clayden , Nick Greeves , Stuart Warren
المصدر:
ORGANIC CHEMISTRY
الجزء والصفحة:
ص690
2025-07-08
470
The Wittig reactions below were all used in the synthesis of natural products. You will notice that some reactions are Z selective and some are E selective. Look closer, and you see that the stereoselectivity is dependent on the nature of the substituent on the carbon atom of the ylid.
We can divide ylids into two types: those with conjugating or anion-stabilizing substituents adjacent to the negative charge (such as carbonyl groups) and those without. We call the first sort stabilized ylids because the negative charge is stabilized not only by the phosphorus atom but by the adjacent functional group—we can draw an alternative enolate-type structure to represent this extra stabilization. The rest we call unstabilized ylids.
●The stereochemistry of the Wittig reaction The general rule is: • with stabilized ylids the Wittig reaction is E selective
• with unstabilized ylids the Wittig reaction is Z selective.
الاكثر قراءة في مواضيع عامة في الكيمياء العضوية
اخر الاخبار
اخبار العتبة العباسية المقدسة
