Acetic alkyl phosphines

A number of methods were also developed for removing iodide impurities from acetic anhydride, such as syn-gas stripping [68], extraction in the presence of phenyl or alkyl phosphines [69], the use of lower fatty acids in combination with rhodium recovery [70], the use of silver-containing ion-exchangers [71], or oxidation with hydrogen peroxide [72]. 

Air oxidation of a variety of aliphatic and alkyl aromatic compounda air oxidation of p-nitrotoluene sulfuric acid substitution chlorination of a variety of organic compounds reaction between isobutylene and acetic acid oxidation of ethylene to acetaldehyde (Wacker processes) hydrochlorination of olehns absorption of phosphine in an aqueous soluhon of formaldehyde and hydrochloric acid acehc acid from the carbonylation of methanol oxidation of tri-alkyl phosphine dimerization of olefins. 

A detailed reaction proving the nucleophilic attack was shown for platinum complexes [25]. The aUcoxide coordinated to platinum attacks phosphorus while the carbon atom coordinated to platinum migrates to phosphorus. Thermodynamically the result seems more favorable, but mechanistically this shuffle remains mysterious (see Figure 8). Coordination to platinum makes the phosphorus atom more susceptible to nucleophilic attack, and the harder atoms (P and O) and softer ones (C and Pt) recombine as one might expect. The same mechanism was proposed by Matsuda [22] for the decomposition of triphenylphoshine by palladium(II) acetate. In this study the aryl phosphines are used as a source for aryl groups that are converted into stilbenes via a Heck reaction. Even alkyl phosphines underwent P-C bond cleavage via palladium acetate. 

The asymmetric allylic phosphination of allylic acetate derivatives proceeded under mild conditions to afford chiral phosphines in good to excellent yields (Scheme 4.10) [26]. The catalyst system was comprised of commercially available materials including a common palladium source and JosiPhos as the chiral ligand. The enantioselectivity of the process was outstanding (up to 96% ee), and the conditions were quite mild (40 C). While only a single alkyl phosphine was screened, these results provided the proof of concept for the process, and extending the chemistry to more complex substrates and phosphorus... 

Examples are given of common operations such as absorption of ammonia to make fertihzers and of carbon dioxide to make soda ash. Also of recoveiy of phosphine from offgases of phosphorous plants recoveiy of HE oxidation, halogenation, and hydrogenation of various organics hydration of olefins to alcohols oxo reaction for higher aldehydes and alcohols ozonolysis of oleic acid absorption of carbon monoxide to make sodium formate alkylation of acetic acid with isobutylene to make teti-h ty acetate, absorption of olefins to make various products HCl and HBr plus higher alcohols to make alkyl hahdes and so on. 

Notable examples of general synthetic procedures in Volume 47 include the synthesis of aromatic aldehydes (from dichloro-methyl methyl ether), aliphatic aldehydes (from alkyl halides and trimethylamine oxide and by oxidation of alcohols using dimethyl sulfoxide, dicyclohexylcarbodiimide, and pyridinum trifluoro-acetate the latter method is particularly useful since the conditions are so mild), carbethoxycycloalkanones (from sodium hydride, diethyl carbonate, and the cycloalkanone), m-dialkylbenzenes (from the />-isomer by isomerization with hydrogen fluoride and boron trifluoride), and the deamination of amines (by conversion to the nitrosoamide and thermolysis to the ester). Other general methods are represented by the synthesis of 1 J-difluoroolefins (from sodium chlorodifluoroacetate, triphenyl phosphine, and an aldehyde or ketone), the nitration of aromatic rings (with ni-tronium tetrafluoroborate), the reductive methylation of aromatic nitro compounds (with formaldehyde and hydrogen), the synthesis of dialkyl ketones (from carboxylic acids and iron powder), and the preparation of 1-substituted cyclopropanols (from the condensation of a 1,3-dichloro-2-propanol derivative and ethyl-... 

Chiral phosphinous amides have been found to act as catalysts in enantio-selective allylic alkylation. Horoi has reported that the palladium-catalyzed reaction of ( )-l,3-diphenyl-2-propenyl acetate with the sodium enolate of dimethyl malonate in the presence of [PdCl(7i-allyl)]2 and the chiral ligands 45 gave 46 in 51-94% yields and up to 97% ee (Scheme 38). It is notorious that when the reaction is carried out with the chiral phosphinous amide (S)-45a, the product is also of (S) configuration, whereas by using (R)-45b the enantiomeric (R) product is obtained [165]. 

Phosphinous amides, based on proline and tetrahydroisoquinoline carboxylic acid, bearing a second donor center (50, Ar=Ph R =H, CH3,Tr, Ph R =H, CH3,Tr, Ph and 51, R =H,Tr R =H,Tr) (Scheme 40) have been developed for use in allylic alkylation and amination of substituted propenyl acetates, yielding the corresponding products in 87-98% (5-94% ee) and 29-97% (14-93% ee) respectively [55, 167]. With bidentate ligands of type 38 where R=(S)-PhMeCH, and with the bis(aminophosphanes) 52 (R=Ph) similar allylic alkylations have been also tested [168,169]. 

Reaction rates have first-order dependence on both metal and iodide concentrations. The rates increase linearly with increased iodide concentrations up to approximately an I/Pd ratio of 6 where they slope off. The reaction rate is also fractionally dependent on CO and hydrogen partial pressures. The oxidative addition of the alkyl iodide to the reduced metal complex is still likely to be the rate determining step (equation 8). Oxidative addition was also indicated as rate determining by studies of the similar reactions, methyl acetate carbonylation (13) and methanol carbonylation (14). The greater ease of oxidative addition for iodides contributes to the preference of their use rather than other halides. Also, a ratio of phosphorous promoter to palladium of 10 1 was found to provide maximal rates. No doubt, a complex equilibrium occurs with formation of the appropriate catalytic complex with possible coordination of phosphine, CO, iodide, and hydrogen. Such a pre-equilibrium would explain fractional rate dependencies. 

The chiral ir-allyl-Pd(II) intermediates shown in Scheme 84 undergo epimerization. The efficiency of this step and the regiochemistry of the nucleophilic attack to the exo face are very important for obtaining enantioface selection (Scheme 89). Bosnich analyzed the general characteristics of the asymmetric alkylation in terms of the properties of the allylic acetate substrates and of the 7T-allyl-Pd(II) intermediates, which undergo facile o-tc-o rearrangement, readily switching the face of Pd coordination (208). Examination of the dynamic equilibria of a series of cationic ir-allyl-Pd-chiral phosphine complexes has indicated that the 7r-allyl intermediates epimerize 10-100 times faster than the nucleo-... 

Takemoto and coworkers extended their palladium-catalyzed asymmetric allylic alkylation strategy using allyl acetate and chiral phase-transfer catalyst to the quaternization of 13 [23b]. A correct choice of the achiral palladium ligand, (PhO P, was again crucial to achieve high enantioselectivity and hence, without chiral phosphine ligand on palladium, the desired allylation product 15 was obtained with 83% ee after hydrolysis of the imine moiety with aqueous citric acid and subsequent benzoylation (Scheme 2.12). 

Alkyl ethers of sucrose have been prepared by reaction with long-chain alkyl halides to provide mixtures of regioisomers and products of different degree of substitution.82,83 A similar reaction with chloromethyl ethers of fatty alcohols provides formaldehyde acetals.84,85 Alkenyl ethers of various carbohydrates, and notably of sucrose, can also be obtained by palladium-catalyzed telomerization of butadiene (Scheme 6).86 88 Despite a low-selectivity control, this simple and clean alternative to other reactions can be carried out in aqueous medium when sulfonated phosphines are used as water-soluble ligands. 

Preparation of alkyldiphenylphosphine oxides. General procedure from phospho-nium salts. Triphenyl phosphine is heated under reflux with an excess of alkyl halide. The precipitated phosphonium salt is filtered off, washed well with ether, and then heated with 30 per cent w/w aqueous sodium hydroxide (c. 4 ml/g) until all the benzene has distilled out. The mixture is cooled and extracted with dichloromethane, and the extracts are dried (magnesium sulphate) and evaporated to dryness. In this way ethyldiphenylphosphine oxide is obtained from triphenyl phosphine (65.6 g, 0.25 mol) and iodoethane (42.9 g, 0.275 mol) in dry toluene (250 ml) to give first the phosphonium salt (102.4 g, 97.9%) after 3.5 hours, from which the phosphine oxide is obtained as needles (53.2 g, 92.5%), m.p. 123-124 °C (from ethyl acetate) p.m.r. 5 (CDC13, TMS) 1.9-13 (m, 10H, Ph2PO), 2.3 (m, 2H, CH2) and 1.2 (dt, 3H, JHm, = 7 Hz, JMeP = 17 Hz, Me). 

A new phosphine ligand 5.21 has been synthesized and employed by Zhang and co-workers. in the Pd-catalyzed enantioselective alkylation of 2-cyclohexenyl ester. The ligand can differentiate quite effectively between the R- and S-enantiomers of acetates. 

One of the first mechanistic proposals for the hydrocarboxylation of alkenes catalyzed by nickel-carbonyl complexes came from Heck in 1963 and is shown in Scheme 24. An alternate possibility suggested by Heck was that HX could add to the alkene, producing an alkyl halide that would then undergo an oxidative addition to the metal center, analogous to the acetic acid mechanism (Scheme 19). Studies of Rh- and Ir-catalyzed hydrocarboxylation reactions have demonstrated that for these metals, the HX addition mechanism, shown in Scheme 24, dominates with ethylene or other short-chain alkene substrates. Once again, HI is the best promoter for this catalytic reaction as long as there are not any other ligands present that are susceptible to acid attack (e g. phosphines). 

ALKYL SELENOCYANATES Triphenyl-phosphine-Diethyl azodicarboxylate. ALKYNES Acetic anhydride-Pyridine. Dimethyl) diazomethyl)phosphonate. OrganoUthium reagents. 

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