Other Synthetic Routes

Chemical vapor deposition (CVD) is a solvent-free process and is discussed in Section 4.1. 

Ihble II. Some Examples of PPVs Prepared via Methoxy-Substituted Precursor Polymers 

The infrared (IR) spectrum of unsubstituted PPV has been studied in detail and assignments made to almost all the observed bands [75]. The most relevant ones are Usted in Ikble IV. 

The absorptions at approximately 965 (6c-H frons-vinylene) and 700 cm ( c-H ciy-vinylene) can be helpful in the characterization of mixtures of cis- and tmns-PFV, normally obtained via Wittig reaction, as well as in monitoring a cis-to-trans isomerization process. The 6c-H out-of-plane bends for substituted ben- 

Tkble IV. Main Absorptions Observed in PPVIR Spectrum 

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Pyrrohdinone (2-pyrrohdone, butyrolactam or 2-Pyrol) (27) was first reported in 1889 as a product of the dehydration of 4-aminobutanoic acid (49). The synthesis used for commercial manufacture, ie, condensation of butyrolactone with ammonia at high temperatures, was first described in 1936 (50). Other synthetic routes include carbon monoxide insertion into allylamine (51,52), hydrolytic hydrogenation of succinonitnle (53,54), and hydrogenation of ammoniacal solutions of maleic or succinic acids (55—57). Properties of 2-pyrrohdinone are Hsted in Table 2. 2-Pyrrohdinone is completely miscible with water, lower alcohols, lower ketones, ether, ethyl acetate, chloroform, and benzene. It is soluble to ca 1 wt % in aUphatic hydrocarbons. 

Other synthetic routes to pyrazinones and quinoxalinones are from the halo compounds, by dealkylation of ethers (8lJCS(Pl)3111> or by diazotization of the corresponding amines, but since the halo derivatives are normally derived from the hydroxy compounds, and the amines from the halo derivatives, direct synthesis seems to represent the most practical approach. 

Triphenylisoxazole can be synthesized by the condensation of 1,4-dilithiodeoxyben-zoin oxime with Af,fV-dimethylbenzamide (78JOC3015) and from the rearrangement of triphenylisoxazoline fV-oxide (369) in aqueous alcoholic sodium hydroxide (24JA2105). A number of other synthetic routes to triphenylisoxazole have been reported (62HC(i7)i, p. 57) but these are of relatively iftinor importance. 

Butadiene can be alternatively produced by other synthetic routes discussed with the synthesis of isoprene, the second major diolefin for rubber production. 

The reaction described is of general synthetic utility for the preparation of a variety of cyclic /3-keto esters from the corresponding ketones. Using this procedure the 2-carbethoxy-cycloalkanones have been prepared from cyclononanone, cyclo-decanone, and cyclododecanone in yields of 85%, 95%, and 90%, respectively. The procedure is simpler and gives much higher yields than other synthetic routes to these systems. 

There are other synthetic routes to halides similar to compounds (39), which are direct precursors of six-membered cyclic nitronates (35) (Scheme 3.36). 

Two other synthetic routes to derivatives of this ring system should be mentioned here, and the transformations are shown in Scheme 54. The phenanthrene-fused fV-aryldihydro[1.2.4]triazine 274 was found to undergo 1,3-dipolar cycloaddition with diarylnitrilimine to give the cycloadduct 275 <1997J(P1)1047. This transformation is entirely analogous to that taking place with a fused oxadiazine derivative, as discussed in Section 11.19.6.1. 

Other synthetic routes to phosphazenes, using phosphorus(v) compounds as substrates, are more limited. An example of the reaction of a nitrile with a phos-phorus(v) chloride is provided by Scheme 4.48 In benzene solution, or in the absence... 

Imides - Polyimides (PI) have been conventionally prepared by the chemical or thermal cyclodehydration of polyamic acids formed from the solution reaction of aromatic tetracarboxylic dianhydrides and aromatic diamines. The early PI were insoluble and relatively intractable. The polyamic acid was the processable intermediate. However, the polyamic acid precursor has two major shortcomings, hydrolytic instability and the evolution of volatiles during the thermal conversion to PI. In addition, residual solvent was left in adhesive tapes and prepregs to obtain tack, drape and flow. During the fabrication of components, the evolution of volatiles caused processing problems and led to porosity in the part. As work progressed on PI, other synthetic routes were investigated (e.g. reaction of esters of aromatic tetracarboxylic acids with diamines... 

Organic chemistry has many diversified synthetic methods the ion-radical methods are among them. This chapter shows the features and specific advantages of ion-radical approaches to needed compounds, having no intention to strike out other synthetic routes. 

The Pd-catalyzed C-C coupling (Sonogashira coupling) was applied to polymer synthesis about 20 years ago [23-25], and has especially been developed for the synthesis of n-conjugated poly(aryleneethynylene)s (PAEs) (for reviews, see refs. [16,26-33]). Recently other synthetic routes for PAEs were also developed, e.g., the alkyne metathesis method [28, 34] and the coupling reaction of =C-MR3 with R X (M=Si [35, 36] or Sn [37, 38]). In this review, we are concerned with the synthesis and chemical properties of PAEs with heteroaromatic rings. 

While the reduction of amides to aldehydes competes successfully with other synthetic routes leading to aldehydes, reduction of amides to alcohols is only exceptionally used for preparative purposes. One such example is the conversion of trifluoroacetamide to trifluoroethanol in 76.5% yield by catalytic hydrogenation over platinum oxide at 90° and 105 atm [7770]. 

Two similar syntheses have been reported by Ziegler and co-workers (487) and Kametani et al. (488,489). Reaction of N-methylisatic anhydride (584) with thioacetamide afforded glomerin (60) in 58% yield (487). The other synthetic route is as follows The sulfinamide (585), prepared from N-methylanthranilic anhydride and thionyl chloride, was treated with acetamide and propionamide to afford glomerin (60) and homoglomerin (61), respectively (Scheme 72) (488,489). 

Pentacene can be efficiently prepared by reduction of pentacenequinone by an aluminium-cyclohexanol mixture (Goodings et al, 1972). A scheme of this synthesis is shown in Fig. 2.1. Other synthetic routes with good overall yields have also been reported. 

Other synthetic routes to the carbapenem ring system include photolytic Wolff rearrangement (73JCS(P 1)2024), aldol condensation (78JA313), addition-cyclization (80JOC1135) and /3-lactam formation (78JOC4438,79TL4359). An excellent review of carbapenem synthesis has recently appeared (82H(17)463). 

Other synthetic routes to benzazepines involving ring expansion of six-membered heterocycles include the action of diazomethane (77CPB321), sulfonium ylides (77H(7)37> or acyl halides (75T1991) on quaternary 3,4-dihydroisoquinolines that of sulfoxonium ylides on quaternary quinolines (74IJC(B)1238) and the zinc-acetic acid reduction of quaternary 1-acyltetrahydroisoquinolines (77BSF893). Photoaddition of acyl- or aryl-nitrenes to the exocyclic alkene bond of 2-methylene-1,2-dihydroquinolines results in ring expansion to... 

Several other synthetic routes also exist. The stereospecific Syntex process is an example using chiral technology to produce enantiomerically pure naproxen ... 

The synthesis of ternary transition metal nitrides through the reaction of two binary nitrides (Table 8.1, Reaction 1) or by nitriding two metals (Table 8.1, Reaction 2) has been relatively unsuccessful. Consequently, until recently, there was little or no information concerning the synthesis and structures of these phases. Lately, several transition metal ternary nitrides have been made through other synthetic routes, such as metathesis reactions and ammonolysis. For example, the ternary nitride CuTaN217... 

Biosynthetic processes Elongation of RNA or DNA chains Other synthetic routes RNA polymerase I DNA polymerase Poly(ADP-ribose)polymerase Carbamoyl phosphate synthetase Anthranilate synthase-phosphoribosyl transferase Glycogen synthetase Methionyl-tRNA synthetase ATP phosphoribosyl transferase Zn2+... 

This reaction is reported to be much more difficult to perform than it appears. According to Rajan et al. 72) the mechanism is not typical of polycondensations, since appreciable amounts of high polymer are present at low conversions and unreacted monomer is found at high conversions. Numerous other synthetic routes have been described. According to Cleary 71) the only other process which has been unequivocally demonstrated to give the required polymer is the self condensation of alkali metal salts of 4-halothiophenols, as described by Lenz et al. 73). 

Other synthetic routes are of course possible. One of the earliest approaches used a Grignard reaction to attach the side chain. 

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