Three-step procedure

In spite of the instability of polyamic acid solutions, the two-step procedure via polyamic acid has been the most frequently used because of its high utihty and the low cost. 

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The 5-oxohexanal 27 is prepared by the following three-step procedure (1) 1,2-addition of allylmagnesium bromide to an a, / -unsaturated aldehyde to give the 3-hydroxy-1,5-diene 25, (2) oxy-Cope rearrangement of 25 to give 26, and (3) palladium catalyzed oxidation to afford 27. The method was applied to the synthesis of A -2-octalone (28), which is difficult to prepare by the Robinson annulation[25]. 

In 2000, an efficient three-step procedure for the synthesis of 5-substituted 3-isoxazolols (without formation of undesired 5-isoxazolone byproduct) was published. The method uses an activated carboxylic acid derivative to acylate Meldrum s acid, which is treated with A,0-bis(ten-butoxycarbonyl)hydroxylamine to provide the N,0-di-Boc-protected P-keto hydroxamic acids 14. Cyclization to the corresponding 5-substituted 3-isoxazolols 15 occurs upon treatment with hydrochloric acid in 76-99% yield. 

Cleavage of the chiral auxiliary is effected in a three-step procedure commencing with quatemization of the nitrogen with methyl fluorosulfonate, methyl trlfluoromethanesulfonate, or trimethyloxonium tetrafluoroborate. Reduction of the corresponding iminium salt 19 with NaBH4 and acidic hydrolysis of the resulting product affords substituted aldehyde 5 without epimerization of either stereocenter. 

This compound is prepared from ethyl orthoformate and hippuric acid by a convenient three-step procedure, c/. ref. 1. 

The second approach for the synthesis of 2-amino-3-hydroxycarboxylic acids starts with a chiral isothiocyanate which is added, via the tin enolate, to aldehydes. The initially formed adducts are immediately derivatized to the heterocycles, from which. yj 7-2-amino-3-hy-droxycarboxylic acids result after a three-step procedure. The diastereomeric ratios of the intermediate bis-heterocyclic products range from 93 7 to 99 1 (desired isomer/sum of all others)104. 

Vinyl- and acetylenic tricarbonyl compounds are reactive dienophilic components in Diels-Alder reactions. Cycloadditions of these compounds with substituted butadienes were recently used to develop a new synthetic approach to indole derivatives [14] (Scheme 2.9) by a three-step procedure including (i) condensation with primary amines, (ii) dehydration and (iii) DDQ oxidation. 

The catalyst played an important role in the asymmetric synthesis of Corey lactone based on high diastereofacial selective Diels-Alder reaction between chiral acrylate 37 and 5-benzyloxymethylcyclopentadiene [41] (Equation 3.9). The cycloadduct 38 was then converted into chiral Corey lactone [42] by a three-step procedure. 

These salts are obtained from 1,2 (or l,3)-diamines. The cyclization step is generally the condensation of the diamines on ethyl orthoformate in the presence of ammonium tetrafluoroborate (Scheme 19). By using enantiop-ure diamines, chiral salts 34 bearing stereogenic centers on the backbone, on the nitrogen substituents, or on both were prepared [1,2,4,5,26]. Several dicyclophane imidazolinium salts have been prepared by one-pot three-step procedure [27]. 

At the end of this three-step procedure we have generated a graph (i.e., a subgraph of the process graph) whose edges indicate the flow of species Jt, and whose nodes contain the chemical jc, at the given operating state. 

For this micro reactor version, the catalyst was coated on the AlMg3 platelet as a thin silver layer by sputtering [43,44], A further set of platelets was covered with an a-alumina layer by sol-gel technique and impregnated by a three-step procedure with silver lactate. 

Figure 1. Three step procedure of the carbonization of PVC by UV and laser irradiation...

J. Vuorinem and J. Turunen, A three step procedure for assessing bioequivalence in the general mixed model framework, Stat. Med., 15, 2635 (1996). 

Ferrocene Monomers. Although the isopropenylferrocene monomer has been reported previously by several groups of investigators,34-37 we were able to develop a more facile, dependable, high yield synthesis for this compound, utilizing the three-step procedure shown below ... 

The synthesis of luminescent organoboron quinolate polymers (21) (Fig. 15) via a three-step procedure starting from a silylated polystyrene has been communicated. The synthesis was initiated by the highly selective borylation of poly (4-trimethylsilylstyrene) (PS-Si), followed by the replacement of the bromine substituents in poly(4-dibromoborylstyrene) (PS-BBr) with substituted thienyl groups (R = H, 3-hexyl, 5-hexyl). In the final step, the 8-hydroxyquinolato moiety was introduced. The hexyl-substituted polymers efficiently emitted light at 513-514nm upon excitation at 395 nm.40... 

A more sophisticated method was developed by Ren et al. [123] for the immobilization of penicillin G acylase by covalent grafting in the interlayer galleries of a LDH by a three-step procedure using a glutamate pillared LDH as the starting material. 

A preferable, three-step, procedure for preparing anhydrous bis(2,4-pentanedionato)zinc, m.p. 127°, in good yields involves (1) the preparation of bis(2,4-pentanedionato)zinc hydrate from zinc sulfate heptahydrate and 2,4-pentanedione in aqueous solution in the absence of heat, (2) conversion of the bis(2,4-pentanedionato)zinc hydrate into a bis (2,4-pentanedionato) zinc-methanol adduct, and (3) decomposition of the methanol adduct. 

Because both enantiomers, (+) and (-)-camphoric add, are available by oxidation either from natural (+)-D-camphor or from natural (-)-L-borneol, both enantiomers of camphanoyl chloride can be prepared conveniently.3 5 The corresponding enantiomers of camphanic acid were described for the first time by Wreden6and Aschan.7 The three-step procedure, described above is an adaptation of procedures described by Aschan,8 Zelinsky et al.,9 Meyer et al.,10 and Gerlach.3... 

As a continued effort to prepared hexameric systems based on the self-assembly of directed bw-terpyridine monomers, several interesting in families, e.g. 43, of iron and ruthenium connectivity have appeared <06DMP413, 06DT3518>. But in the assembly process, the creation of a three-step procedure to the novel first nondendritic fractal 44 entitled the "Sierpinski hexagonal gasket" was reported <06MI1782>. 

The self-consistent field ca 1 c u la t i o ns ( 1 3 ) are carefully guided by experiment through the following three step procedure (1 ) determination of the many-... 

The first demonstration of fluorous synthesis was in the preparation of small (8-12 members) isoxazo-line and isoxazole libraries by the three-step procedure outlined in Figure 8.1461 All reactions were purified by three-phase liquid-liquid extraction. The starting substrates were simple allylic alcohols which were tagged with the fluorous silyl halide 5 to make substrates 6 for an ensuing dipolar cycloaddition. This was conducted by the Mukaiyama method with a large excess of nitro compound and... 

A stoichiometry calculation is thus essentially a three-step procedure in which 1) the weight of D is divided by its formula weight to get moles of D, 2) the moles of D are converted to the moles of A by multiplying by the mole ratio a/d, as found in the chemical equation, and 3) the moles of A are converted to grams of A by multiplying by the formula weight of A. 

At this point, the final specifications for the one or two chosen product(s) after selection process should be identified. This can be done using a three-step procedure. First, we define the product micro and macrostructure. Second, we rank the product s most important attributes, an effort that forces a review of how the product will be used. Third, we review any chemical triggers, that is, chemical stimuli which cause major changes in product properties. Finally, we turn to the manufacture itself, which relies on technical know-how of thermodynamics, chemical reaction kinetics, transport phenomena, and unit operations. Some of these ideas are illustrated in the following example. Except for a schematic of the manufacturing process, the many details related to the manufacturing plant are omitted in this discussion. 

The three-step procedure described for the preparation of the illustrated crotylsilanes is initiated with the hydrosilation of rac-3-butyn-2-ol. This procedure is significantly improved with respect to the positional selectivity of the hydrosilation resulting in exclusive formation of the racemic (E)-vinylsilane, and as a result the present procedure is much more amenable to scale-up than those previously described in the literature.8 The enzymatic resolution of the racemic secondary allylic alcohol (vinylsilane) has also been reported using commercially available lipase extracts. The use of a Johnson ortho ester Claisen rearrangement affords the (E)-crotylsilanes 4 in nearly enantiomerically pure form. 

Selective monoalkylation of methyl aryl-acetates by alkylhalides is difficult with conventional bases. It may be achieved by application of the three-step procedure outlined above adding (33) to the methyl arylacetates at a low temperature... 

The augmented Lagrange multiplier algorithm finds the energy minimum of the constrained problem with an iterative, three-step procedure ... 

We follow a three-step procedure First, we must find how equilibrium composition, rate of reaction, and product distribution are affected by changes in operating temperatures and pressures. This will allow us to determine the optimum temperature progression, and it is this that we strive to approximate with a real design. Second, chemical reactions are usually accompanied by heat effects, and we must know how these will change the temperature of the reacting mixture. With this information we are able to propose a number of favorable reactor and heat exchange systems—those which closely approach the optimum. Finally, economic considerations will select one of these favorable systems as the best. 

This approach to defining cost therefore proposes a three-step procedure for the evaluation of new pharmaceutical products. Assume that there is some threshold value V for cost per QALY that appropriately governs resource allocation. 

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