Phosphorus‐Bearing Lithium Compounds in Modern Synthesis

Crystal, Solution, and Computational Study of the Structure of Ortho‐Lithium N,N‐Diisopropyl‐P,P‐Diphenylphosphinothioic Amide

“…Coalescence was reached at À 90 °C and below this temperature two broad signals began to emerge, which were clearly distinguishable at À 110 °C with δ P 78.05 and 76.14 ppm in an approximate ratio of 52 : 48 (Figure S4). No 31 P, 7 Li scalar coupling could be resolved even at the lowest temperature measured. The 1 H NMR spectrum (Figures 4a and S2) showed the expected signals for a monosubstituted Pphenyl ring and an ortho-substituted P-aryl system (see Table 1 and the Supporting Information for proton assignments).…”

“…The sample of recrystallized 12 contained a small amount of phosphinothioic amide 10 due to partial hydrolysis of the anion. The structural characterization is based on the NMR spectra of a 0.32 M sample measured at À 30 °C mimicking the DoLi conditions of 10, except for the 7 Li and NOE NMR spectra. In these cases, the analysis is performed on the sample of recrystallized 12, which is free from the excess of TMEDA as well as from the non-deuterated solvent and lithium salts of the n BuLi solution used in the deprotonation.…”

“…The lithium-bearing carbon atom C2 appeared as a very broad signal, barely distinguishable above the noise of the spectrum. The lack of a resolved 13 C, 7 Li coupling prevented to gain insight into the aggregation state. [33b] Fortunately, this information could be obtained by NOE experiments measured at 0 °C.…”

“…For clarity, H atoms have been omitted. Selected bond lengths [Å] and angles [°]: P1À S1 1.982(6), P1À N1 1.683(6), P1À C1 1.853(8), P1À C7 1.820(6), Li1À S1 2.46(1), Li1À C2 2.12(2), Li1À N2 2.14(1), Li1À N3 2.11(1), C1À C2 1.391 (7), C2À C3 1.43(1), C1À P1À S1 112.9(2), N1À P1À C7 103.2(3), P1À S1À Li1 95.0(3), S1À Li1À C2 93.0(5), N2-Li1À C2 134.7(6), C2À Li1À N3 117.7(6), N2À Li1À N3 83.9(5), S1À L1À C2À C1 5.0(7), S1À P1À C1À C2 À 14.8(6), Li1À N2À C18À C19 À 38.4(6), Li1À N3À C19À C18 À 37.7(6), N2À C18À C19À N3 54.6 (7). to lithiated carbon (H3) and methyl protons of the i Pr moiety.…”

“…[6] Although P-based DMGs have been comparatively less studied, a number of phosphorus-centered directing groups containing a P=X moiety (X=C, N, O, S) have proven their effectiveness in ortho-CÀ H functionalization processes via DoLi. [7] These include phosphoranes, [8] phosphazenes, [9] phosphine oxides, [8a,10] phosphinic acids, [11] phosphinic amides, [12] phosphinothioic amides, [13] phosphinimidic amides, [14] phosphonates, [15] phosphonic amides, [16] phosphonamidates, [17] phosphonothioic diamides, [18] phosphoramides [19] and phosphorodiamides. [20] The applications of the ortho-lithiated species as building blocks in organic synthesis are greatly enhanced by their behavior as bidentate and tridentate ligands very useful for the preparation of main group, transition metal and rare earth complexes via methatetic reactions [21] including the synthesis of P-stereogenic derivatives.…”