Phosphine 2- ethyl

H-Phosphinates 54 may also serve as precursors for phosphonamidates 56 (Scheme 18).l63 74 75] In the simplest procedure, a N-protected H-phosphinate 54 (produced, for example, by the Baylis procedure,156 see Section 10.10.1.2) is treated with a mixture of CC14, TEA, and the desired amino component. The H-phosphinates are converted in situ into phosphonochloridates 52, which are then trapped by the amine component. Sampson and Bartlett 761 reported improved yields when the H-phosphinate was first treated with bis-(trimethylsilyl)acetamide (BTMSA) to produce the trivalent species 55. They also noted that the reactions are generally cleaner when phosphinate ethyl esters are used instead of phosphinate methyl esters, presumably because the latter are more prone to nucleophilic demethylation. 

Figure 25 Molecular structure of C6o[Pt(PEt3)2]6- The phosphine ethyl groups have been omitted for clarity. (Reprinted with permission of the American Chemical Society from P.J. Fagan et al )...

SYNS DICHLOROETHYLPHOSPHINE DICHLORO-METH i L PHOSPHINE ETHYL PHOSPHONOUS DICHLORIDE, anhydrous (DOT) TL 373... 

Photolytic decomposition of peroxides is not v y efBcient in crosslinking. An enhancement effect on the extent of photocrosslinking of polyolefins in the presence of peroxides is displayed by aromatic hydrocarbons such as naphthalene. These transfer the exdtation energy absorbed to a peroxide. This procedure, however, does not represent an important improvement when compared with that refored to earlier, namely the photoreduction of pdyethylene with aromatic ketones and quinones [84. From aromatic ketones and quinones, particulariy bena>phenone [32], chlorinated benzophenones, benzoyl-l-( dohexanol [82], a, -dimethot - hen acdr henone, 2,4,6-trimethyl benzoyl phenyl phosphinic ethyl ester [85], anthrone [86], anthraqui-none [87], naphthoquinone, benzoquinone, and their d vatives have all been examined. 

Randall et al. (34) obtained the chemical shifts and coupling constants for tertiary phosphines in l,3-dialkylimidazolin-2-ylidene carbene complexes. Jz p-M-c(earbene) trms was found to be much larger than the two bond cis coupling constant. In addtion, Jnp-ciZ) in the phosphine ethyl and propyl groups was found to be less than 2.4 Hz which is small when compared to the uncomplexed ligand value of 13 to 15 Hz. 

Phosphites, such as triisopropyl and triphenyl phosphite, are weaker electron donors than the corresponding phosphines, but they are used in some reactions because of their greater rr-accepting ability. The cyclic phosphite trimethylol-propane phosphite (TMPP) or 4-ethyl-2,6,7-trioxa-l-phosphabicyclo[2.2.2]oc-tane (8), which has a small cone angle and small steric hindrance, shows high catalytic activity in some reactions It is not commercially available, but can be prepared easily[27]. 

The benzoic acid derivative 457 is formed by the carbonylation of iodoben-zene in aqueous DMF (1 1) without using a phosphine ligand at room temperature and 1 atm[311]. As optimum conditions for the technical synthesis of the anthranilic acid derivative 458, it has been found that A-acetyl protection, which has a chelating effect, is important[312]. Phase-transfer catalysis is combined with the Pd-catalyzed carbonylation of halides[3l3]. Carbonylation of 1,1-dibromoalkenes in the presence of a phase-transfer catalyst gives the gem-inal dicarboxylic acid 459. Use of a polar solvent is important[314]. Interestingly, addition of trimethylsilyl chloride (2 equiv.) increased yield of the lactone 460 remarkabiy[3l5]. Formate esters as a CO source and NaOR are used for the carbonylation of aryl iodides under a nitrogen atmosphere without using CO[316]. Chlorobenzene coordinated by Cr(CO)j is carbonylated with ethyl formate[3l7]. 

Resorcinol carboxylation with carbon dioxide leads to a mixture of 2,4-dihydroxyben2oic acid [89-86-1] (26) and 2,6-dihydroxyben2oic acid [303-07-1] (27) (116). The condensation of resorcinol with chloroform under basic conditions, in the presence of cyclodextrins, leads exclusively to 2,4-dihydroxyben2aldehyde [95-01-2] (28) (117). Finally, the synthesis of l,3-bis(2-hydroxyethoxy)ben2ene [102-40-9] (29) has been described with ethylene glycol carbonate in basic medium (118), in the presence of phosphines (119). Ethylene oxide, instead of ethyl glycol carbonate, can also be used (120). 

In contrast, if the olefin is more stericaHy hindered (branched) and/or the reaction is operated at a higher pressure (4 MPa), formation of the primary and secondary phosphines is favored as in the reaction with 2,4,4-trim ethyl -1 -pen ten e [107-39-1]. 

Ethyl (triphenylphosphoranylidene)acetate is available from FIuka AG and Trldom Chemical Inc. under the name (ethoxycarbonylmethylene)triphenyl-phosphorane and from Aldrich Chemical Company, Inc. under the name (carbethoxymethylene)triphenylphosphorane. The reagent may be prepared from triphenyl phosphine and ethyl bromoacetate by the following procedure. ... 

A 1-L, two-necked, round-bottomed flask fitted with a dropping funnel and a mechanical stirrer is charged with 131.0 g (0.5 mol) of triphenyl phosphine (FIuka AG, purum) and 250 mL of benzene (Merck, pro analysi). The solution is stirred vigorously while 83.5 g (0.5 mol) of ethyl bromoacetate (FIuka AG,... 

The initiation mechanism is well defined because of the recent isolation and spectroscopic characterization of the initial zwitterion from ethyl cyanoacrylate (ECA) and a phosphine [8,9]. Specifically, zwitterion 4 was prepared from the reaction of equimolar amounts of dimethylphenyl phosphine, 5, and ECA, 6,... 

Apart from tertiary amines, the reaction may be catalyzed by phosphines, e.g. tri- -butylphosphine or by diethylaluminium iodide." When a chiral catalyst, such as quinuclidin-3-ol 8 is used in enantiomerically enriched form, an asymmetric Baylis-Hillman reaction is possible. In the reaction of ethyl vinyl ketone with an aromatic aldehyde in the presence of one enantiomer of a chiral 3-(hydroxybenzyl)-pyrrolizidine as base, the coupling product has been obtained in enantiomeric excess of up to 70%, e.g. 11 from 9 - -10 ... 

This salt is prepared, by a procedure analogous to that employed for the methyl salt, from ethyl bromide and triphenyl phosphine (Chapter I , Section II). 

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-... 

An interesting parallel was found while the microwave-enhanced Heck reaction was explored on the C-3 position of the pyrazinone system [29]. The additional problem here was caused by the capability of the alkene to undergo Diels-Alder reaction with the 2-azadiene system of the pyrazinone. An interesting competition between the Heck reaction and the Diels-Alder reaction has been noticed, while the outcome solely depended on the substrates and the catalyst system. Microwave irradiation of a mixture of pyrazinone (Re = H), ethyl acrylate (Y = COOEt) and Pd(dppf)Cl2 resulted in the formation of a mixture of the starting material together with the cycloaddition product in a 3 1 ratio (Scheme 15). On the contrary, when Pd(OAc)2 was used in combination with the bulky phosphine ligand 2-(di-t-butylphosphino)biphenyl [41-44], the Heck reaction product was obtained as the sole product. When a mixture of the pyrazinone (Re = Ar) with ethyl acrylate or styrene and Pd(dppf)Cl2 was irradiated at 150 °C for 15 min, both catalytic systems favored the Heck reaction product with no trace of Diels-Alder adduct. 

Dichloroethylphosphine has been shown to react with methyl vinyl ketone to form 2-ethyl-5-methyl-A -l,2-oxaphospholen-2-oxide (25), which has been converted to (26) by chlorination in the presence of base. The same phosphine adds to methyl acrylate in the presence of acetic acid to give the phosphine oxide (27). Further examples have appeared of the reactions of the phenylhydrazones of methyl ketones with phosphorus trichloride to produce the heterocycles (28). 

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