Redox Active and Redox Neutral Transformations of Titanocene and Phosphorus

In 1990, German Professor Dieter Seebach explained in his Angewandte editorial the necessity of furthering the field of organic chemistry and the downfalls to accepting this field as a mature sciences stating the following: “We have not witnessed the discovery of a new aldol, Beckman, Claisen, Cope, Diels -Alder, Mannich, Michael, or Wittig reactions; even the exploitation of strain effects in small rings and the broader application of 1,3-dipolar cycloadditions, dithiane methodology, ortho metallation, the acyloin, the pinacol condesations, photochemical and radical reactions, nucleophilic substitution, and umpolung reactivity took place without the discovery of new modes of reactivity. Nevertheless, each of the transformations cited has, in a sense, been raised to a much higher level of sophistication.” In our research group, we emphatically pursue this enhancement of sophistication in the fundamental reactivity of reagents. Specifically, we are interested in the synthesis of highly substituted carbon centers by both transition metal and phosphorus-mediated pathways, as these are essential to the construction of many molecules of biological activity and medicinal interest. Rapid access to these centers can allow for convergent and facile approaches to desired targets. Classically, these moieties are synthesized using multistep sequences, and frequently employing expensive transition metals. Our group focuses on the one-pot construction of these centers by employing underdeveloped reactivity of phosphorus and inexpensive transition metals. Herein, we discuss recent advances towards these ends in regards to the formation of C–C, C–N, C=C, and C–P bonds.