Additions to carbonyl groups can be diastereoselective even without rings
المؤلف:
Jonathan Clayden , Nick Greeves , Stuart Warren
المصدر:
ORGANIC CHEMISTRY
الجزء والصفحة:
ص858-859
2025-07-20
587
Additions to carbonyl groups can be diastereoselective even without rings
What happens if we bring the stereogenic centre closer to the carbonyl group than it was in the last example? You might expect it to have a greater influence over the carbonyl group’s reactions. And it does. Here is an example.
There is three times as much of one of the two diastereoisomeric products as there is of the other, and the major (anti) diastereoisomer is the one in which the nucleophile has added to the front face of the carbonyl group as drawn here. We can make these same two diastereo isomers by addition of an organometallic to an aldehyde. For example, this Grignard reagent gives three times as much of the syn diastereoisomer as the anti diastereoisomer. The major product has changed, but the product still arises from attack on the front face of the carbonyl as shown.
These two reactions are not nearly as diastereoselective as most of the reactions of cyclic compounds . But we do now need to explain why they are diastereo selective at all, given the free rotation possible in an acyclic molecule. The key, as much with acyclic as with cyclic molecules, is conformation.
الاكثر قراءة في مواضيع عامة في الكيمياء العضوية
اخر الاخبار
اخبار العتبة العباسية المقدسة
