Bicyclic phosphines

Fig. 15.13 Bicyclic phosphines used in cobalt-catalyzed hydroformylation.

The isomeric bicyclic phosphines (41) have been obtained by reduction with trichlorosilane of the related isomeric phosphine oxides, the reaction proceeding with... 

HP IR measurements have recently been reported by workers at Sasol for cobalt-catalysed 1-dodecene hydroformylation reactions using bicyclic phosphines (4) derived from (R)-(+)-limonene [68]. Using Fourier deconvolution to separate absorptions due to [HCo(CO)4] and [Co2(CO)7(phosphine)], it was possible to estimate the ratio of modified [HCo(CO)3(phosphine)] to un-modified [HCo(CO)4] in the catalytic mixture, using peak areas. Values of this ratio ranged from ca. 2-20, depend-... 

The chiral bicyclic phosphines 5 (and in particular 5a [7b]) are currently the most active phosphorus-based acylation catalysts, enabling use of low reaction temperatures. Under these conditions (i.e. —40 °C) selectivity factors as high as 370-390 were achieved (Scheme 12.2). This is the best selectivity factor ever reported for metal-free, non-enzymatic kinetic resolution. As a consequence, very good enantiomeric purity of both the isobutyric esters 7 and the remaining alcohols 6 was obtained, even at substrate conversions approaching 50% (Scheme 12.2) [7, 8],... 

Later, the chiral bicyclic phosphine catalyst 5a was also used for kinetic resolution of allylic alcohols with isobutyric anhydride [8, 9]. The best results were obtained for trisubstituted allylic alcohols - selectivity factors ranged from 32 to 82 at -40 °C. 

Hydrolysis of 1,1-diphenylphosphorinanium bromide 71 with aq NaOH gave phosphine oxide 72 in 99% yield. Phosphine oxide was further reductively alkylated to 73 using Si(0Et)3H/Ti(0-7Pr)4 with various alkyl bromides <1998SL497> (Scheme 3). Bicyclic phosphines 74 were alkylated to 75 using BuLi/RBr (Equation 4) <2003JCD2036, 2003JCD4669>. 

Palladium-catalyzed nucleophilic substitutions of activated allylic alcohols have been investigated using a bicyclic phosphine as the chiral element. Reactions have been reported with racemic acyclic allylic acetates <1999TL7791> and cycloalkenyl carbonates <2001TL1297> using the phosphine 203, with good to excellent enantiomeric excesses. 

The first example of a chiral nucleophilic promoter that is also capable of catalytic turnover was described by Vedejs et al.[8], who showed that acylation of 2a with ACjO in the presence of the C2-symmetric phospholane 6 (2a Ac20 6 = 1 2.5 0.16) gave 4 with ee = 34 % (44 % conversion,, v = 2.7, s = fas/ siow) while racemic 1 -phenyl-2,2-dimethylpropanol was acylated with m-chlorobenzoic anhydride under the same reaction conditions to yield the corresponding ester 7 with ee = 81 % (25 % conversion, 5=12-15). In a continuation of these studies the bicyclic phosphine 8 was prepared and evaluated (Scheme 2) [9]. It was found that 8 is an efficient catalyst for the resolution... 

By Addition o/P—H to Unsaturated Compounds. There has been a marked reduction in the number of papers concerned with this route in the past year, but nevertheless a number of interesting studies have been reported. Thus, for example, the primary phosphine (21) undergoes free-radical-induced intramolecular cyclization to form the bicyclic phosphine l-phosphabicyclo[3,3,l]nonane (22). ... 

When these bicyclic phosphinates were irradiated at 254 nm in acetonitrile containing ethanol as a trapping agent, fragmentation was complete in 1-2 hours. Examination of the reaction solutions by NMR (CDCI3) showed that the major products were the expected ethyl alkyl methylphosphonates in one case (30, R = Et, 8 30.7), the identity was confirmed by ip NMR comparison with a known sample. However, in... 

As indicated by their pattern of reactivity,the products of pyrolysis of the Of-diazomethylphosphines (92) are best regarded as nucleophiliccarbenes (93). Some aspects of the reactivity of the bicyclic system (94) have been explored. With chlorodiethylphosphine, the salt (95) is formed, which is converted into the bicyclic phosphine oxide on methanolysis. The phosphine... 

Quin s group have reported the synthesis of a number of tricyclic phospholene oxides, e.g., (9), by the McCormack reaction. The isomeric bicyclic phosphine... 

The energies for structures along the reaction coordinate for hydrolysis of the bicyclic phosphinate [54] are detailed in Scheme 15. Analysis of the TBP intermediates and SP transition states for exocyclic cleavage in the base-catalysed hydrolysis of the cyclic urea phosphonate [24a] takes account of the increased effective electronegativity of the methylene ligand in this system (Scheme 16). The calculations for [24] vividly illustrate that what is perceived as a disallowed pseudorotation is shown to be energetically favourable by careful analysis and application of relative apicophilicities. 

The [4-1-2]-cycloaddition reaction of phospholes 243 and furan derivatives 244 with various dienophiles catalyzed by palladium complexes 240 led to the formation of a number of chiral bicyclic phosphines 245-251, which are interesting as chiral P-ligands (Scheme 79) [146, 153]. 

Figure 1.3 Bicyclic phosphines used as standard ligands in Co-catalyzed hydroformylation.

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