Other Synthetic Methods

During the past ten years, two valuable alternatives to the Grignard and alkali-metal-organophosphide syntheses of tertiary phosphines have been developed. By choosing the appropriate route and reagents, one should now be able to tailor-make polydentate ligands to incorporate just about any electronic and/or steric effects desired. 

King et developed a route to poly(tertiary phosphines) by use of a base-catalyzed addition of a phosphorus-hydrogen bond to the carbon-carbon double bond of various vinylphosphine derivatives the first extensive series of methylated polyphosphines were prepared this way. The synthesis of unsymmetrical diphosphines of the type i 2PCH2CH2P(CH3)2 involves addition of a P-H bond to CH2=CHP(S)(CH3)2 via potassium tert-bwioxxdQ catalysis, followed by desulfurization with LiAlH4 in boiling dioxane (i.e.. Equations 10,11). 

Variations of the base-catalyzed method were used to prepare the three tritertiary phosphines i P(CH2CH2PR2)2 (R = CH3 or CeHs, R = CeHs R = CeHs, R - CH3), the mixed aliphatic-aromatic, open-chained tetratertiary phosphine, 20, the branched pentatertiary phosphine, 21, 

Radical-Catalyzed P-H Addition to Vinyl and Allyl Compounds 

The radical-catalyzed method for preparation of mixed PP, PAs, PS, and PN combinations in polydentate ligands is noteworthy, as it represents 

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The reaction of 2-aminothiazoles with alkyl isothiocyanates yields 2-thiazolylthioureas (30.3, 490), otherwise usually obtained by direct heterocyclization (Chapter II. Section II.4). Other synthetic methods... 

The mechanism of the polycondensation reaction remains unclear. A vanety of possible reactive intermediates have been suggested, including sdyl radicals and sdyl anions. An anionic propagation mechanism (100,101,103) has been strongly suggested, although the case is by no means setded (104). Other Synthetic Methods. 

Information on the synthesis of the polyetherimide—polysiloxane block copolymers has not been disclosed. Many other synthetic methods for preparing block copolymers have been described (19,20,25) but are currendy not beheved to be commercially important. 

Other synthetic methods have been investigated but have not become commercial. These include, for example, the hydration of ethylene in the presence of dilute acids (weak sulfuric acid process) the conversion of acetylene to acetaldehyde, followed by hydrogenation of the aldehyde to ethyl alcohol and the Fischer-Tropsch hydrocarbon synthesis. Synthetic fuels research has resulted in a whole new look at processes to make lower molecular weight alcohols from synthesis gas. 

Other synthetic methods are also known for uhich a book of icfercnce must be consulted. 

The other major route to quinone diazides is based on the alkaline hydrolyses of mono-4-toluenesulfohydrazones of quinones, which will be discussed in Section 2.6. In the same section other synthetic methods are briefly discussed. 

Group IIB-Transition- and Inner-Transition-Metal Bonds 8.3.3.S. Other Synthetic Methods... 

Because of their usefulness in aldol additions and other synthetic methods (see especially Section 6.4.2.3), there has been a good deal of interest in the factors that... 

A number of matrices have also been used for the preparation of semiconductor nanoparticles, whereby the particulate material is grown within and subsequently fills the cavities of the host material. These includes zeolites,361 glasses,362 and molecular sieves,363-365 and can be viewed as nanochambers which limit the size to which crystallites can grow. Other synthetic methods include micelles/microemulsions,366-369 sol-gels,370,371 polymers,372-377 and layered solids.378... 

Several B-haloborazines have been prepared by photochemical reactions. B-monochloroborazine was prepared photochemically by Oertel and Porter using a number of chlorinating reagents (HCl, CH3a, CHa3, HSO3CI). Other synthetic methods reported for this compound and for B-monobromoborazine involve the for-... 

Because of their usefulness in aldol additions and other synthetic methods (see especially Section 6.5.2), there has been a good deal of interest in the factors that control the stereoselectivity of enolate formation from esters. For simple esters such as ethyl propanoate, the /r-enolate is preferred under kinetic conditions using a strong base such as LDA in THF solution. Inclusion of a strong cation solvating co-solvent, such as HMPA or tetrahydro-1,3 -dimethyl-2(1 Z/)p y r i m i d o nc (DMPU) favors the Z-enolate.13... 

No other synthetic method Is known that achieves the equivalent transformation. Rather elaborate procedures using an allylic anion type of the homoenolate "equivalents" or homoenolate radicals have been reported, but their tolerance to the structure of the enone acceptor is much narrower. 

Before we go through the organometalUc or metal organic route to the synthesis of nanoparticles, a brief description of other synthetic methods is given below. 

Aerosol processes afford materials having an optimum phase purity as contrasted to catalysts prepared by other synthetic methods. In addition, their syntheses are reproducible and metal ion concentrations are predictable based on starting... 

There are a wide variety of other synthetic methods for the preparation of oxetanes however, most of these are not very general. They frequently require starting materials which are difficult to prepare, and rarely give high yields (never as high as the better photochemical preparations). It is clear then that in comparison with the alternative methods of oxetane synthesis, the photocycloaddition reaction is more generally useful and convenient. This synthetic utility justifies a brief description of experimental conditions. 

B. Comparison of Metal Atom with Other Synthetic Methods. 86... 

All BMI building blocks and maleimide-terminated oligomers discussed previously are synthesized from the corresponding polyamine precursor and maleic anhydride simply because of economic reasons. However, there are other synthetic methods available, for instance, the reaction of a functionalized monomaleimide with a polyfunctional monomer or oligomer. Such a functionalized monomaleimide is maleimido benzoic acid or its acid halide. These were used to synthesize maleimide-terminated polyamides (39, 40) or polyesters (41), respectively. 

C-Acylation of the lithium enolates derived from 4-methoxybut-3-en-2-ones is achieved with acid chlorides without any significant O-acylation. A general route to pyranones results which avoids the acidic conditions frequently associated with other synthetic methods (80TL1197). Cyclization of these products, which exist in an enolic form, occurs at room temperature in benzene in the presence of a trace of trifluoroacetic acid (Scheme 135). 

Several synthetic methods for the synthesis of methyleneamido complexes have been developed. The only method which shows any degree of generality is the use of metalloketimines. The other synthetic methods listed below have not been studied in depth. 

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