ACYL- AND ALKYLIDENEPHOSPHINES. XXI.¹Acylphosphines and Their Derivatives with Phosphorus Atoms of Coordination Number 3, 2, and 1

Pyrido‐Annulated 1,3‐Azaphospholes: Synthesis of 1,3‐Azaphospholo[5,4‐b]pyridines and Preliminary Reactivity Studies

“…In an attempt to crystallize crude 5c by overlayering the concentrated thf solution with n ‐hexane, the single‐crystalline phosphaalkene dimer 6c with 1,3‐diphosphetane structure was obtained. The dimerization of 3c to 6c represents an alternative reaction of the intermediates 3 known for acyclic phosphaalkenes17 but detected here for the first time for 1,3‐azaphosphole precursors (Scheme ).…”

PhP=CPh2 and Related Phosphaalkenes: A Solution Equilibrium between a Phosphaalkene and a 1,2‐Diphosphetane

“…In the absence of a crystal structure, this compound had previously been assigned as the 1,3‐diphosphetane . The regioselective [2+2] cyclodimerization of phosphaalkenes is well‐established, and affords either the head‐to‐tail (i.e., 1,3‐diphosphetane) or the head‐to‐head product (i.e., 1,2‐diphosphetane) , , . Dimer 2a was fully characterized by using 31 P, 1 H and 13 C{ 1 H} NMR spectroscopy, mass spectrometry and elemental analysis.…”

“…[16] The regioselective [2+2] cyclodimerization of phosphaalkenes is well-established, and affords either the head-totail (i.e., 1,3-diphosphetane) or the head-to-head product (i.e., 1,2-diphosphetane). [16,20,[22][23][24][25][26][27][28][29][30][31][32][33][34] Dimer 2a was fully characterized by using 31 P, 1 H and 13 C{ 1 H} NMR spectroscopy, mass spectrometry and elemental analysis. The molecular structure of 2a, shown in Figure 3, reveals that the sterically favorable anti-configuration of the adjacent P-Ph moieties is adopted.…”

Expanding the Analogy Between P=C and C=C Bonds to Polymer Science

“…However, in this case the phosphaalkene tautomer 7 (enol) is formed quantitatively because of the relative weakness of the P-Si bond in the acylphosphine 6 relative to the strong Si-O bond in 7. From a preparative standpoint, this method is probably the most convenient and versatile route to phosphaalkenes with minimal steric protection [37][38][39][40][41][42][43]. The rearrangement reaction can also be exploited to prepare phosphaalkenes with a-positioned nitrogen or sulfur atoms.…”