18899-20-2Relevant academic research and scientific papers
Hindered organoboron groups in organic chemistry. 24. The condensation of aliphatic aldehydes with dimesitylboron stabilised carbanions to give ketones
Pelter, Andrew,Smith, Keith,Elgendy, Said M. A.,Rowlands, Martin
, p. 7104 - 7118 (1993)
The condensation of boron stabilised carbanions, MeS2BCHLiR1, (R1≠H) with aliphatic aldehydes, R2CHO, followed by treatment with trifluoroacetic anhydride (TFAA) or N-chlorosuccinimide (NCS) is an unique, broadly applicable redox process that yields ketones, R1CH2COR2, directly and in high yields. The anion MeS2BCH2Li (MeS2BCHLiR1, R1=H) gives high yields of alkenes, R2CH=CH2 in the same conditions.
Increasing Olefin Metathesis Activity of Silica-Supported Molybdenum Imido Adamantylidene Complexes through E Ligand σ-Donation
Nater, Darryl F.,Paul, Bhaskar,L?tsch, Lukas,Schrock, Richard R.,Copéret, Christophe
, (2021/09/29)
Molybdenum imido adamantylidene complexes with different substituents on the imido ligand (dipp=2,6-diisopropylphenyl, ArF5=C6F5, and tBu) having distinct electron donating abilities were investigated for the metathesis of internal and terminal olefins, for both molecular and silica-supported species using standardized protocols. Here we show that surface immobilization of these compounds results in dramatically increased activity compared to their molecular counterparts. Additionally, we show that electron withdrawing imido groups increase the activity of the compound towards terminal olefins while they simultaneously decrease the ability to metathesize internal olefins. Furthermore, these systems also show high stability when used as initiators in olefin metathesis, although the species that display higher initial activity deactivate faster than those that show more a more moderate reaction rate at first. Our catalytic studies, augmented by DFT calculations, show that all investigated compounds have a remarkably small energy difference between the trigonal bipyramidal (TBP) and square planar (SP) configurations of the metallacyclobutane intermediates, which has previously been linked to high activity.
Benchmarked Intrinsic Olefin Metathesis Activity: Mo vs. W
Zhizhko, Pavel A.,Mougel, Victor,De Jesus Silva, Jordan,Copéret, Christophe
, (2018/02/28)
Combining Surface Organometallic Chemistry with rigorous olefin purification protocol allows evaluating and comparing the intrinsic activities of Mo and W olefin metathesis catalysts towards different types of olefin substrates. While well-defined silica-supported Mo and W imido-alkylidenes show very similar activities in metathesis of internal olefins, Mo catalysts systematically outperform their W analogs in metathesis of terminal olefins, consistent with the formation of stable unsubstituted W metallacyclobutanes in the presence of ethylene. However, Mo catalysts are more prone to induce olefin isomerization, in particular when ethylene is present, probably because of their propensity to undergo more easily reduction processes.
