Regioselective Cross-Metathesis Reaction Induced by Steric Hindrance

Abstract

[reaction: see text] When hexa-1,5-dien-3-ol is protected with bulky groups, a regioselective cross-metathesis reaction can take place at the C5-C6 double bond.

Synthesis and Structural Revision of Cyslabdan

“…Therefore, we attempted the stepwise synthesis of 28. The Wittig reaction of 22 with Ph 3 P=CH 2 afforded olefin 29 in high yield, which was subjected to cross metathesis with methacrolein in the presence of Grubbs second-generation catalyst [34][35][36][37][38] to afford the desired aldehyde 28, which was also subjected to Wittig reaction with Ph 3 P=CH 2 to give epoxydiene 21. Finally, the coupling of epoxydiene 21 with N-acetyl-L-cysteine under mild basic conditions afforded (8R)-cyslabdan (2).…”

The First Total Synthesis of Topsentolide B3

“…In this case, the reaction was highly Z-selective, and there was no spectroscopic or chromatographic evidence for the formation of either the E-isomer or other side products. Indeed, to the best of our knowledge, this is the first example of a selective RCM reaction, [17] demonstrating the formation of the lactone ring in the synthesis of the oxylipins class of compounds or any other medium ring lactones. All the intermediate products were well characterized using NMR spectroscopy and mass spectrometry.…”

A Metathesis Approach for the Preparation of Polyhydroxylated Compounds as Head Groups in Surfactant Synthesis

“…Several reports on cross metathesis with substrates containing allylic alcohols or ethers have been published lately, although it is unclear whether allylic alcohols or ethers facilitate the metathesis of the adjacent double bond or rather have an adverse effect on the reaction. [22][23][24][25] As part of our synthetic plan, we therefore decided to initiate a brief investigation on alcohol protectinggroup strategies for the outcome of a metathesis reaction. Olefin 4a therefore served as starting material for compounds 4b and 4c, which have different protecting-group constellations.…”