Phosphonation catalysed

The complex lr(H)(Cl)[P(0)(OCH3)2][P(OH)(OCH3)2]3 obtained from [lrCl(C8Hi4)2l2 and dimethyl H-phosphonate catalyses the stereoselective reduction of 4-fert-butylcyclo-hexanone to 97/3 cis/trans 4-/crt-butylcyclohexanol [128], This complex also catalyzes the... 

Scheme 19.30 A mmetric Mukaiyama-Michael additions of silyl enol ethers to a,p-unsaturated atyl phosphonate catalysed by bis(8-quinolinolato)-Al complex.

Bacillus cereus degrades (45) to acetaldehyde with fission of the C—P bond. An enzyme which catalyses the decomposition of phosphono-acetaldehyde (47), an intermediate in this degradation to acetaldehyde, has been characterized. The enzyme will only degrade (47) and will not breakdown a number of other phosphonates, including phosphonomycin (48). ... 

The peroxide-catalysed addition of dimethyl phosphonate to norborna-diene gives nortricyclenes as well as norbornenes. Usually, radicals react with this diene to give only nortricyclene derivatives. The ease of hydrogen abstraction from the parent phosphonate undoubtedly favours trapping of radical (8). 

Two types of racemic 3-hydroxy phosphonates, in which the phosphono and hydroxy moiehes are separated hy double bond, were successfully resolved using a common enzyme-catalysed acetylation. Both acyclic 52 (Equation 28) and cyclic 54 (Equation 29) derivatives underwent easy acetylation under the kinetic resolution conditions to give the products in high yield and with almost full stereoselechvity. 

This work has been extended to transesterification with secondary alcohols [23], and of phosphonate esters [24], Movassaghi and co-workers have demonstrated that NHCs effectively catalyse the amidation of esters with amino alcohols, although an alternative mechanism involving the NHC acting as a Brpnsted base, resulting in nucleophilic activation of the alcohol for an initial transesterification event, followed by rapid O- to iV-acyl transfer, has been proposed [25, 26],... 

The enzyme FAAH was first identified in the 1980s [39], cloned in the 1990s [25] and more recently, the crystal structure [40] of FAAH bound to methyl arachidonyl phosphonate has been published. The FAAH enzyme has wide substrate specificity capable of catalysing the hydrolysis of a wide variety of... 

Et or Bu) and the phosphonation of iodoaromatics with dialkyl phosphonates, although in this case with poorer yields (better results of the dialkyl arylphosphonates are obtained by photostimulation). Chemical oxidation (using AgNO -peroxodi-sulphate) and anodic oxidation of aromatics in the presence of trialkyl phosphites produces dialkyl arylphosphonates in good yields. The Cul-catalysed arylation of dialkyl (cyanomethyl)-phosphonates affords dialkyl (a-cyanobenzyl)phosphonates. ... 

SnCl catalyses the formation of the (a-aryloxybenzyl) phosphonates (62) from diethyl trimethylsilyl phosphite and... 

Pd(PPh )2 12 catalyses the internal alkylation of the phosphonate esters (96) and the formation of the 3-methyiene-l-oxa-2-phosphacycl.oalkane 2-oxides (97 ) phosphorus-containing analogues of a-methylenelactones. Further examples of the... 

Figure 10.25 Effect of phosphate stabiliser on Fe(m)-catalysed decomposition of hydrogen peroxide in absence of substrate [237]. Initial concentration 2.9 g/l H202, Phosphonate stabiliser 2 g/l, 95 °C, pH 12...

Table 4 Kinetic parameters for those antibodies raised against phosphonates [88-91] which effect the resolution of the fluorinated alcohols [84-87]. The configuration of the disastereoisomerically pure product from each antibody-catalysed process was shown to correspond to that of the antibody-inducing hapten.

Fig. 41 The monoclonal, 6D9, raised against phosphonate [124] catalysed the hydrolysis of one possible regio-isomer [125] of a phenacetyl ester prodrug derived...

Tetraphenylcyclopent-3-enone and dimethyl phosphonate are the major products from the base-catalysed reaction of methyl phosphonate with tetra-cyclone.75 A mechanism involving initial hydride transfer from dimethyl phosphinate anion to the ketone followed by kinetically controlled protonation to give (98) is suggested. 

When a solution of the ester (155 R = H) in dioxan is warmed at 80 °C, the phosphonate (156) is produced together with about 5% yields of each of dimethyl hydrogen phosphonate and diazoacetoacetic ester (Scheme 8) the enol phosphate (157) could not be detected. The explanation for this sequence of reactions also relies on proton mobility, and the reaction is known to be acid-catalysed.124... 

In order to generate antibodies which catalyse the hydrolysis of carbonates (6, 10), carboxylic esters (9) and amides with a certain degree of specificity, the phosphates (7a. lOai and phosphonates 9a were used as haptens that mimic the tetrahedral negatively charged transition state of the spontaneous hydrolysis reaction (see Scheme 11.3) [27] [29]. 

Quantitative NMR examination of the hydrolysis of dimethyl phosphonate (245) using 0-enriched water under base-catalysed conditions supports a mechanism involving P—O rather than C—O bond cleavage. 

A comparison has been made" of various monoterpenoid rearrangements cataiysed by either zirconium phosphates or by zirconium organo-substituted phosphonates, and acid-catalysed rearrangements of a-trans- and /3-cis-3,4-epoxycaranes have been described." It has been observed" that on exposure to Li (OBu )3AlH, perhydro-naphthalene-l,4-diol monosulfonate ester (269) rearranges to the 11-oxatricyclo-[5.3.1.0.2,6]undecane derivative (270) (see Scheme 88). 

List was the first to explore this possibility, examining the Hantzsch ester mediated reduction of a,P-unsaturated aldehydes [209], Using 20 mol% of the binaphthyl derived phosphonate salt of morpholine (153) in dioxane at 50 °C, a series of P-aryl a,P-unsaturated aldehydes underwent transfer hydrogenation with Hantzsch ester 154 with excellent levels of absolute stereocontrol (96-98% ee) (Scheme 63). The method was also applied to the aliphatic substrates ( )-citral and famesal to give the mono-reduced products in 90% and 92% ee, respectively. Significantly, in line with many of the chiral secondary amine catalysed transformations described above the reactions follow a simple and practical procedure without the need for exclusion of moisture and air. 

Scheme 6 System used by Wulff to catalyse the hydrolysis of carbonate (32) imprinting the cavities with the TSA phosphonate (31)...

A different approach was used by Emgenbroich and Wulff [42] to develop imprinted polymers with enantioselective esterase activity. The system was based on the use of an amidinium functional monomer (33), already developed earlier by the same group, but in this case a chiral phosphonate (62) was used as imprinting TSA in order to catalyse the hydrolysis of the corresponding chiral ester (63). The polymer imprinted with the L-enantiomer was able to enhance the esterolytic activity 325-fold when compared with the background and 80 times compared to the non-imprinted polymer. The ratio between the two rates constant, Lai-i/L ii-i) = 1 -4, can be taken as a measure of the enantioselective efficiency of the reaction. 

By using Josiphos ligands, palladium-catalysed hydrophosphorylation of norbomen-es with hydrogen phosphonates proceeds efficiently to give the corresponding phos-phonates in high enantioselectivities.90... 

The methanolyses of several phosphate/phosphonate esters and their thio analogues [e.g. 0,0-diethyl 0-(4-nitrophenyl) phosphate, paraoxon (101 X = O, Z = 4-N02), 0,0-diethyl S- S-dichlorophenyl) phosphorothioate, (102 R = OEt), and 0-ethyl S-OA-dichlorophenyl) methylphosphonothioate (102 R = Me)] catalysed by methoxide and the complex of Zn2+ (MeO-) with 1,5,9-triazacyclododecane (79 M = Zn) were studied in methanol at 25 °C. The reaction of methoxide and (79 M = Zn) with the entire series of esters appears to adhere to a common mechanism that involves pre-equilibrium binding of the substrate, followed by intramolecular attack of the coordinated methoxide concerted with OAr or SAr leaving group departure.79... 

Copper catalysed addition of a (3-zincated phosphonate to an electrophile preparation of dimethyl 2-(cyclohex-1-en-3-on-1-yUpentanephosphonate10... 

---