Catalytic Wittig Reactions of Semi‐ and Nonstabilized Ylides Enabled by Ylide Tuning

Abstract

The first examples of catalytic Wittig reactions with semistabilized and nonstabilized ylides are reported. These reactions were enabled by utilization of a masked base, sodium tert-butyl carbonate, and/or ylide tuning. The acidity of the ylide-forming proton was tuned by varying the electron density at the phosphorus center in the precatalyst, thus facilitating the use of relatively mild bases. Steric modification of the precatalyst structure resulted in significant enhancement of E selectivity up to > 95:5, E/Z.

New Insights into the Mechanism of Reduction of Tertiary Phosphine Oxides by Means of Phenylsilane

“…It should also be mentioned that 1‐phenylphospholane oxide is converted into 1‐phenylphospholane via an activation barrier, which is a few kcal/mol lower than in the case of similar reduction involving tri‐ n ‐butylphosphine oxide. This observation correlated well with the recent results from the Krenske group . Our experiments also show that a similar kinetic effect stimulates electron withdrawing groups in the phenyl ring of silane .…”

Electroreduction: A Sustainable and Less Energy‐Intensive Approach Compared to Chemical Reduction for Phosphine Oxide Recycling to Phosphine

“…[15] The most common strategies of obtaining TPP from recycling of TPPO are by using chemical reductants like silyl hydrides, [16] aluminium hydrides, [17] boranes, [18,19] and so on. [15,[20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37] The bond dissociation energy of the PÀ Cl bond (H 2 PÀ Cl, 315.1 kJ/mol) is less than that of the PÀ O bond (H 2 PÀ OH, 359.7 kJ/mol). Therefore, chlorination of TPPO by oxalyl chloride and/or phosgene followed by reduction by hydrogenation at high pressure in presence of metal catalysts (Pt, Rh, Pd, Na, Fe, Al) remained an alternative approach.…”

Direct Carboxylation of Electron‐Rich Heteroarenes Promoted by LiO‐tBu with CsF and [18]Crown‐6

“…(1)). [32,33] To confirm the role of [tBuOCO 2 M] in the presentc arboxylation, the reactions of 1a and 1f were conducted with the pre-prepared [tBuOCO 2 Li], CsF,and [18]crown-6 under an Ar atmosphere. As expected, the carboxylated products 2a and 2f were obtained in 99 and 92 %y ields, respectively (Scheme 2).…”