104764-65-0Relevant academic research and scientific papers
An examination of the scope and stereochemistry of the Ireland-Claisen rearrangement of boron ketene acetals
Seizert, Curtis A.,Ferreira, Eric M.
, p. 4460 - 4468 (2014/05/06)
The Ireland-Claisen rearrangement of boron ketene acetals is described. The boron ketene acetal intermediates are formed through a soft enolization that obviates the use of strong bases and the intermediacy of alkali metal enolates. Yields and diastereoselectivities of these rearrangements are very sensitive to the choice of boron reagent, even among those that have been shown to effect quantitative formation of boron ketene acetals from esters. The rearrangement occurs at room temperature for all substrates with generally high levels of stereoselectivity. In contrast to previous reports using boron triflates, the use of a commercially available boron iodide reagent allows for a wider substrate scope that extends to propionates and arylacetates, as well as the previously described α-oxygenated esters. This work also provides insight into the dynamic nature of boron ketene acetals and the ramifications of this behavior for reactions in which they are intermediates. Borane down: Boron enolates of allylic esters are efficiently generated at -78 °C using cHx2BI (dicyclohexyliodoborane)·Et3N. These rearrange smoothly on being warmed to room temperature to give generally high diastereoselectivity in forming γ,δ-unsaturated acids (see scheme). The rearrangements provide a key insight into the dynamic nature of boron ketene acetals.
INTERCEPTION OF TETRAHEDRAL INTERMEDIATES IN Pd(II)-MEDIATED CYCLOALKENYLATIONS OF OLEFINIC ENOL ETHERS
Kende, Andrew S.,Wustrow, David J.
, p. 5411 - 5414 (2007/10/02)
The tetrahedral intermediate 3 has been intercepted during Pd(II)-cycloalkenylation of olefinic enolsilane 1 (R=SiMe2t-Bu).In a related manner, the allyl and crotyl enol ethers 5-8 give with Pd(OAc)2 acetoxy tetrahydrofurans (9, 12, 14, 16), convertible to butyrolactones or furans; competing Pd(II)-mediated Claisen rearrangement was not observed.The intramolecular Pd(II)-cycloalkenylation of the ketene acetal 17 leads to δ-lactones 18 and 19.
