REACT methodology

Collectively, these five elements make up what CORD, the developer of the ABC series, refers to as the REACT methodology, named after the acronym for the five elements encompassed. CORD s teaching materials are specifically designed to support constructivism in the classroom by facilitating the creation of learning environments in which these five elements are encouraged. When the REACT methodology is used effectively, students do not just remember, they understand. 

The applying element of the REACT methodology involves learning by putting concepts to use. In the ABC series, the application exercises often take the form of word problems, not unlike those found in many textbooks. But they are different in two fundamental respects First, they pose realistic (often occupational) situations. Second, they demonstrate the usefulness of academic concepts outside the classroom. Both of these differences add motivation to the learning experience. Consider the following, a typical word problem from a chemistry lesson on pH. 

When the first four elements of the REACT methodology are effectively encouraged, students are able transfer what they learn to unfamiliar contexts. Transferring (the final REACT element) takes place when knowledge is used in a new context or novel situation—one that has not been covered in class. 

These findings are consistent with CORD s years of experience in working with teachers. Time and again, teachers who have worked through CORD s professional development process and have applied the REACT methodology in the classroom over time have expressed enthusiastic approval of the methodology. We close with these words from one of our teacher colleagues ... 

Using this method [the REACT methodology] has really stretched me. 

A further improvement in the cuprate-based methodology for producing PGs utilizes a one-pot procedure (203). The CO-chain precursor (67) was first functionalized with zirconocene chloride hydride ia THF. The vinyl zirconium iatermediate was transmetalated direcdy by treatment with two equivalents of / -butyUithium or methyUithium at —30 to —70° C. Sequential addition of copper cyanide and methyUithium eUcited the /V situ generation of the higher order cyanocuprate which was then reacted with the protected enone to give the PG. 

In a novel approach to vitamin K, Hoffmann-La Roche has exploited the potential acidity at C-3 as a means to attach the side chain of vitamin (36). Menadione was reacted with cyclopentadiene to yield the Diels-Alder adduct. The adduct is treated with base and alkylated at C-3 with phytyl chloride. A retro Diels-Alder reaction yields vitamin K. Process improvements in this basic methodology have been claimed by Japanese workers (37). 

In similar work, CF3CCI2CO2CH3 yields methyl a-trifluoromethyl-a,(i-un-saturated carboxylates when reacted with a zinc-copper couple, aldehydes, and acetic anhydride [67] (equation 55). This methodology gives (Z)-a-fluoro-a- -un-saturated carboxylates from the reaction of carbonyl compounds with CFCI2CO2CH3 and zinc and acetic anhydride [6 ]. 

More recently, Tietze and Steinmetz (96SL667) used the patented polystyrene-resin methodology for for the solid-phase synthesis of a large number of diverse )3-keto esters 40a-h. These were reacted with phenylhydrazine in THF at room temperature to give hydrazones 41a-h that were then cychzed into 2-phenyl 5-substituted pyrazol-3-ones 42a-h by heating in toluene at 1(X)°C (Scheme 12). 

The hetero Diels-Alder [4+2] cycloaddition (HDA reaction) is a very efficient methodology to perform pyrimidine-to-pyridine transformations. Normal (NHDA) and Inverse (IHDA) cycloaddition reactions, intramolecular as well as intermolecular, are reported, although the IHDA cycloadditions are more frequently observed. The NHDA reactions require an electron-rich heterocycle, which reacts with an electron-poor dienophile, while in the IHDA cycloadditions a n-electron-deficient heterocycle reacts with electron-rich dienophiles, such as 0,0- and 0,S-ketene acetals, S,S-ketene thioacetals, N,N-ketene acetals, enamines, enol ethers, ynamines, etc. 

In all the reactions described so far a chiral Lewis acid has been employed to promote the Diels-Alder reaction, but recently a completely different methodology for the asymmetric Diels-Alder reaction has been published. MacMillan and coworkers reported that the chiral secondary amine 40 catalyzes the Diels-Alder reaction between a,/ -unsaturated aldehydes and a variety of dienes [59]. The reaction mechanism is shown in Scheme 1.73. An a,/ -unsaturated aldehyde reacts with the chiral amine 40 to give an iminium ion that is sufficiently activated to engage a diene reaction partner. Diels-Alder reaction leads to a new iminium ion, which upon hydrolysis af-... 

Similar methodology has been applied in the syntheses of 2-amino-3-hydroxycarboxylic acids in high diastereomeric and enantiomeric purity. Two separate pathways give either the antt- or. WM-products. The first strategy relies on haloacetate precursors derived either from (S )-valine 17"- oi or from norephedrine 18102, which are converted into the boron enolates103 and subsequently reacted with aldehydes to deliver. ym-adducts99 102. The diastereomeric ratio, defined as the ratio of the desired diastereomer/the sum of all others, is 50 1 for the former and about 95 5 for the latter adducts. 

A somewhat tedious extension of this methodology, which guarantees good induced stereoselectivity, relies on the reversible introduction of an a-substituent which is removed after the aldol addition is performed. For this purpose, the corresponding derivative of (methyl-thio)acetic acid is converted into the boron enolate and subsequently reacted with aldehydes. The... 

Although the methodology described so far produces <5-oxo esters via diastereoselective enolate additions to enones, the same product may be obtained via an alternate sequence, i.e., addition of ketone or aldehyde enolates to a,j3-unsaturated esters or amides. Enolates of ketones are known to react with a,/ -unsaturated esters to give the Michael adducts50, however, the study of simple diastcrcoselectivity has, so far, been limited to special cases (MIMIRC reactions, Section 1.5.2.4.4.). 

This section presents a variety of reacting flows computed with the LES methodology. The cases presented in this study were chosen, because each features a different aspect of turbulent combustion and also addresses a specific technical difficulty. 

---