Monophosphine adducts

The primary (7, 47) and most commonly used organonickel compounds have been the dimeric 7r-allyl- (or substituted Tr-allyl-) nickel halides (1) (Scheme 1) or their monophosphine adducts (2) in the presence of Lewis acids such as aluminum halides or alkylaluminum halides (4, 48-53). The... 

An interesting variation of the rDA reacdmi is the retro-dimetalla-Diels-Alder reacdmi that generates two reacdve intermediates, o-xylylene (257) and the metal-metal double bonded dimer (256), via a dinu-clear eliminadon. Performing this equilibrium reacdon in the presence of reagents that react with (256), such as trialkylphosphines, yields the dinuclear monophosphine adducts. Consumpdmi of (256) allows the o-xylylene to dimerize as shown in equation (113). ... 

Littke and Fu reported an interesting and important suggestion that commercially available Pd[P(f-Bu)3]2 is a resting state of the system in the HR, and not a catalytically active species. Change of the ratio of Pd to phosphine from 1 1 to 1 2 leads to a marked decrease in the rate of reactions, and the Pd monophosphine adduct PdP(f-Bu)3 is the active catalyst. The combination of Pd[P(t-Bu)3]2 and a phosphine-free Pd complex generates in situ the active 1 1 adduct [7]. 

Standard cyclisation methodology was used to access the cyclic monophosphinic acid derivative 78 by reaction of ammonium phosphonate and ethyldiisopropylamine, followed by the addition of chlorotrimethylsilane, with 2,2 -bis (bromomethyl)-l,l -biphenyl. Silane reduction of 78 gave the secondary phosphine. The secondary phosphine borane complex 79 could be used in alkylation or Michael addition reactions. For example the Michael adduct 80 was produced in high yield by treatment of 78 with a NaH suspension in THF followed by the addition of diethylvinylphosphonate . 

Catalyst 236 is by no means the only one to achieve such results. Helmchen56 uses the manganese-containing monophosphine 245 for alkylation of malonates with racemic allylic chloride 246 to give the adduct 247 that is used in the synthesis of the lactone 248. 

As continuation of this work, a planar chiral [2.2]paracyclophane monophosphine has been applied successfully as an organocatalyst in asymmetric allylic amination of MBH adducts. Up to 71 % ee was achieved using (i )-298 as a catalyst (Scheme 3.127). ... 

The sense of the asymmetric induction was determined by analysing the known monophosphine 23 with R = Me and was independently confirmed by the determination of the crystal structure of the adduct 22, which was... 

Gridnev, I. D. Alberico, E. Gladiali, S. Captured at last A catalyst-substrate adduct and a Rh-dihydride solvate in the asymmetric hydrogenation by a Rh-monophosphine catalyst. Chem. Commun. 2012, 48, 2186-2188. 

Zhang, T.-Z., Dai, L.-X., and Hou, X.-L. (2007) Enantioselective allylic substitution of Morita-Baylis-Hillman adducts catalyzed by planar chiral [2.2] paracyclophane monophosphines. Tetrahedron Asymmetry, 18,1990-1994. 

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