Sequential Electrophilic Substitution Reactions of Tungsten-Coordinated Phosphenium Ions and Phosphine Triflates

Abstract

ion of chloride from [W(CO) 5 {PPhCl 2 }] with AgOSO 2 CF 3 leads to the phosphine triflate complex [W(CO) 5 {PPhCl(OSO 2 CF 3 )}] which undergoes electrophilic substitution reactions with N , N -diethylaniline, anisole, N , N -dimethyl- p -toluidine, toluene, biphenyl, naphthalene, 2,7,9,9-tetramethyl xanthene, and allyltrimethylsilane to form the chlorophosphine complexes [W(CO) 5 {PPhClR}], where R = p -diethylanilinyl, p -anisyl, 2-( N , N -dimethyl-4-methylphenyl), p -tolyl, p -phenylphenyl, 1-naphthyl, 4-(2,7,9,9-tetramethylxanthyl), and allyl. Abstraction of the second chloride with AgOSO 2 CF 3 leads, in most cases, to the respective phosphine triflates [W(CO) 5 {PPhR(OSO 2 CF 3 )}], which react with ferrocene to form the ferrocenyl phosphine complexes [W(CO) 5 {PPhR(C 10 H 9 Fe)}]. The W(CO) 5 unit can be removed via photolysis in the presence of bis(diphenylphosphino)ethane to form metal-free phosphines.

Synthesis of acyl(chloro)phosphines enabled by phosphinidene transfer

“…Similar C-H activation of arenes by phosphorus-containing electrophiles has been described for metal-stabilized phosphenium triates. [42][43][44] Despite its instability in solution, 3[OTf] can be stored in the solid state at À35 C for weeks without decomposition and puried by recrystallization from saturated dichloromethane/ pentane solutions, also at À35 C. Treatment of 3[OTf] with a chloride source (tetra-n-butylammonium chloride) in chloroform at 23 C quantitatively generated 1, [TBA][OTf] and anthracene (Scheme 1). This reactivity is consistent with nucleophilic attack of the phosphonium center in 3[OTf] by chloride, inducing reductive loss of anthracene.…”

Asymmetric Electrophilic Reactions in Phosphorus Chemistry

“…Using this method, chiral phosphine ligands containing primary alkyl, sec-alkyl or aromatic substituents, including ferrocenyl and phenyl groups, were obtained. Phosphine ligands were used in the asymmetric catalytic reduction of alkynes and aldehydes with formation of chiral allyl alcohols with high regioselectivity and full (E)-selectivity as shown in Equation (33) [48]. Reactions of P-chiral secondary phosphine-boranes with fluorobenzene tricarbonylchromium in the presence of sec-butyl lithium led to the formation of phosphine ligands in yields of 75-99% and complete retention of the absolute configuration (Equation (32)) [47].…”

“…Using this method, chiral phosphine ligands containing primary alkyl, sec-alkyl or aromatic substituents, including ferrocenyl and phenyl groups, were obtained. Phosphine ligands were used in the asymmetric catalytic reduction of alkynes and aldehydes with formation of chiral allyl alcohols with high regioselectivity and full (E)-selectivity as shown in Equation (33) [48].…”

“…The reaction of chiral metal phosphides with alkyl halides afforded tertiary phosphine oxides with retention of absolute configuration at phosphorus center (Scheme 7). Several other examples of the stereospecific Michaelis-Becker reaction of sterically hindered Hphosponates with alkyl halides are shown in Equations (48) and (49) [31,37]. 48) (49Cis-and trans-2-methoxy-4-methyl-1,3,2-dioxaphosphorinans react with various sulfenyl chlorides stereospecifically with retention of configuration at phosphorus (Equation (50)).…”

“…Alkylation under conditions of Michaelis Backer reaction.Several other examples of the stereospecific Michaelis-Becker reaction of sterically hindered H-phosponates with alkyl halides are shown in Equations(48) and(49) [31,37]. (Scheme Alkylation under conditions of Michaelis Backer reaction.…”