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.

A study on the deoxygenation of trialkyl‐, dialkyl‐phenyl‐ and alkyl‐diphenyl phosphine oxides by hydrosilanes

“…These problems can be eliminated by applying the phosphine in a catalytic amount, and by insuring the in situ reduction of the phosphine oxide formed. This was first elaborated for the Wittig reaction using silanes as the reducing agent by O'Brien . Since then, the catalytic Wittig reaction has become a hot topic and found a number of applications .…”

The Deoxygenation of Phosphine Oxides under Green Chemical Conditions

“…It has been a challenge to develop catalytic versions of these reactions involving the recycling of the waste cyclic phosphine oxides in in situ reduction [6]. O wide range of phosphine oxides including mainly phospholene-and phospholane derivatives [7][8][9][10]. In these cases, the phosphoranes were formed in situ by the quaternization of the phosphine by the α-haloacetic ester [7][8][9] or even an unactivated alkyl halide [8], followed by dehydrohalogenation by Na 2 CO 3 [7,9], diisopropylethylamine [8], or in situ generated t BuONa [10].…”

“…C 2014 Wiley Periodicals, Inc. Heteroatom Chem. It was found that the deoxygenation with TMDS or PMHS under MW and solvent-free conditions may be the method of choice and provides a green chemical approach.…”

A Biphilic Phosphetane Catalyzes N–N Bond-Forming Cadogan Heterocyclization via PIII/PV═O Redox Cycling

“…In recent years, though, several new catalytic methods involving cycling through phosphine oxide intermediates have emerged, 5 both in redox-neutral 6–7, and redox-driven modes. 8–10 As part of a program aimed at developing designer main group compounds as broadly useful biphilic 11 catalysts in organic synthesis, 12 we recently reported the use of phosphetanes as O -atom transfer catalysts operating via P III /P V =O redox cycling. 12c In this Communication, we advance this biphilic catalysis concept by describing a catalytic N - N bond forming heterocyclization enabled by phosphetane-catalyzed reductive O -atom transfer.…”