31 research outputs found
Structural Diversity of Lithium N âMesitylâ P , P âdiphenylphosphinimidate of the type [(L)Li{OâPPh 2 =NâMes] n Depending on Lewis Base L
Abstract Metalation of N âmesitylâ P,P âdiphenylphosphinic amide with n BuLi in toluene yields tetranuclear lithium N âmesitylâ P , P âdiphenylphosphinimidate ([Ph 2 P(OLi)=NâMes] 4 , 1 ). Metalation of Ph 2 P(O)âN(H)Mes with a mixture of dibutylmagnesium and butyllithium in DME leads to formation of dinuclear [Ph 2 P{OLi(dme)}=NâMes] 2 ( 2 ). Excess of Ph 2 P(O)âN(H)Mes gives dinuclear [Li(OâPPh 2 =NâMes){Ph 2 P(=O)âN(H)âMes}] 2 ( 3 ) with threeâcoordinate alkali ions. The metathetical approach via reaction of 1 with anhydrous magnesium bromide in ethereal solution yields [{(thf)LiBr} 2 {(thf)Li(OâPPh 2 =NMes)(Et 2 O)Li(OâPPh 2 =NMes)}] ( 4 ). Heterobimetallic Li/Mg compounds are not accessible by these protocols. Reactions of 1 with DME, with excess of Ph 2 P(O)âN(H)Mes or with LiBr allows the straightforward conversion to compounds 2 , 3 and 4 .imag
Aves que nidificam em cavidades na Reserva Natural Salto Morato - Guaraqueçaba (PR) /
Orientador : James Joseph RoperDissertaçÄo (mestrado) - Universidade Federal do ParanĂĄ, Setor de CiÄncias BiolĂłgicas, Programa de PĂłs-GraduaçÄo em Ecologia e Conservaçao. Defesa: Curitiba, 2007Inclui bibliografi
Potassium Dimesitylphosphinite Catalyzed Intermolecular Hydrophosphorylation of Alkynes
In this investigation we evaluated
the scope of the intermolecular
hydrophosphorylation (Pudovik reaction) of alkynes R<sup>1</sup>âCîŒCâR<sup>2</sup> (R<sup>1</sup> = H, alkyl, Ph; R<sup>2</sup> = alkyl, Ph,
COOMe, SiMe<sub>3</sub>, SiÂ(<i>i</i>Pr)<sub>3</sub>) with
bisÂ(2,4,6-trimethylphenyl)Âphosphane oxide (dimesitylphosphane oxide,
Mes<sub>2</sub>PÂ(O)ÂH) in tetrahydrofuran at room temperature or 65
°C, catalyzed with 5 or 10 mol % of potassium dimesitylphosphinite
(Mes<sub>2</sub>PâOâK), yielding alkenyldimesitylphosphane
oxides (Mes<sub>2</sub>PÂ(O)âCÂ(R<sup>1</sup>)î»CÂ(H)ÂR<sup>2</sup>). This procedure requires substituents with a âI effect
at the CîŒC triple bond, whereas alkyl-substituted alkynes are
inactive under these reaction conditions. The hydrophosphorylation
proceeds regioselectively, but <i>E</i>/<i>Z</i> isomer mixtures are obtained. <i>E</i>/<i>Z</i> isomerization occurs at elevated temperatures with an estimated
energy barrier of 59 kJ mol<sup>â1</sup> (R<sup>1</sup> = Me;
R<sup>2</sup> = Ph). Trimethylsilyl substituents at the alkyne functionality
(R<sup>1</sup> = H, <i>n</i>Bu; R<sup>2</sup> = SiMe<sub>3</sub>) destabilize the product, leading to degradation and formation
of Mes<sub>2</sub>PâOâSiMe<sub>3</sub> and R<sup>1</sup>âCîŒCâH