Experimental procedures methyl 9-

Many reagents are able to chlorinate aromatic pyrazole derivatives chlorine-water, chlorine in carbon tetrachloride, hypochlorous acid, chlorine in acetic acid (one of the best experimental procedures), hydrochloric acid and hydrogen peroxide in acetic acid, sulfuryl chloride (another useful procedure), etc. iV-Unsubstituted pyrazoles are often used as silver salts. When methyl groups are present they are sometimes chlorinated yielding CCI3 groups. Formation of dimers and trimers (308 R = C1) has also been observed. 

Calmagite. This indicator, l-(l-hydroxyl-4-methyl-2-phenylazo)-2-naphthol-4-sulphonic acid, has the same colour change as solochrome black, but the colour change is somewhat clearer and sharper. An important advantage is that aqueous solutions of the indicator are stable almost indefinitely. It may be substituted for solochrome black without change in the experimental procedures for the titration of calcium plus magnesium (see Sections 10.54 and 10.62). Calmagite functions as an acid-base indicator ... 

An experimental procedure for the conversion of iron(II) phthalocyanine into lithium methyl-(phthalocyanine)ferrate(II) can be found in Houben-Weyl, Vol. 13/9a, p 228. For analogous reactions involving cobalt, see Houben-Weyl, Vol. 13/9b, pp 55, 87. 

Pure di-2-propenylzinc2,8,9 10, bis(2-methyl-2-propenyl)zinc11 or di-2-butenylzinc11 are best prepared by the metal exchange between dimethylzinc and the appropriate triallylborane, which is produced in situ from the Grignard reagent and boron trifluoride-diethyl ether complex. The purification is accomplished by distillation, for experimental procedure, see ref 2, p619. 

The kinetics of the various reactions have been explored in detail using large-volume chambers that can be used to simulate reactions in the troposphere. They have frequently used hydroxyl radicals formed by photolysis of methyl (or ethyl) nitrite, with the addition of NO to inhibit photolysis of NO2. This would result in the formation of 0( P) atoms, and subsequent reaction with Oj would produce ozone, and hence NO3 radicals from NOj. Nitrate radicals are produced by the thermal decomposition of NjOj, and in experiments with O3, a scavenger for hydroxyl radicals is added. Details of the different experimental procedures for the measurement of absolute and relative rates have been summarized, and attention drawn to the often considerable spread of values for experiments carried out at room temperature (-298 K) (Atkinson 1986). It should be emphasized that in the real troposphere, both the rates—and possibly the products—of transformation will be determined by seasonal differences both in temperature and the intensity of solar radiation. These are determined both by latitude and altitude. 

Annual Volume 71 contains 30 checked and edited experimental procedures that illustrate important new synthetic methods or describe the preparation of particularly useful chemicals. This compilation begins with procedures exemplifying three important methods for preparing enantiomerically pure substances by asymmetric catalysis. The preparation of (R)-(-)-METHYL 3-HYDROXYBUTANOATE details the convenient preparation of a BINAP-ruthenium catalyst that is broadly useful for the asymmetric reduction of p-ketoesters. Catalysis of the carbonyl ene reaction by a chiral Lewis acid, in this case a binapthol-derived titanium catalyst, is illustrated in the preparation of METHYL (2R)-2-HYDROXY-4-PHENYL-4-PENTENOATE. The enantiomerically pure diamines, (1 R,2R)-(+)- AND (1S,2S)-(-)-1,2-DIPHENYL-1,2-ETHYLENEDIAMINE, are useful for a variety of asymmetric transformations hydrogenations, Michael additions, osmylations, epoxidations, allylations, aldol condensations and Diels-Alder reactions. Promotion of the Diels-Alder reaction with a diaminoalane derived from the (S,S)-diamine is demonstrated in the synthesis of (1S,endo)-3-(BICYCLO[2.2.1]HEPT-5-EN-2-YLCARBONYL)-2-OXAZOLIDINONE. 

The preparation of macrocyclic diimines and endocyclic enamines are represented by the procedures for the formation of 1,10-DIAZA-CYCLOOCTADECANE and N-METHYL-2-PHENYL-A2-TETRA-HYDROPYRIDINE. Other procedures representative of alkylation reactions and aromaticity (TRI-i-BUTYLCYCLOPROPENYL FLUOROBORATE) round out a volume of tested experimental procedures of general value. 

On the other hand, the method of Mukaiyama can be succesfully applied to silyl enol ethers of acetic and propionic acid derivatives. For example, perfect stereochemical control is attained in the reaction of silyl enol ether of 5-ethyl propanethioate with several aldehydes including aromatic, aliphatic and a,j5-unsaturated aldehydes, with syir.anti ratios of 100 0 and an ee >98%, provided that a polar solvent, such as propionitrile, and the "slow addition procedure " are used. Thus, a typical experimental procedure is as follows [32e] to a solution of tin(II) triflate (0.08 mmol, 20 mol%) in propionitrile (1 ml) was added (5)-l-methyl-2-[(iV-l-naphthylamino)methyl]pyrrolidine (97b. 0.088 mmol) in propionitrile (1 ml). The mixture was cooled at -78 °C, then a mixture of silyl enol ether of 5-ethyl propanethioate (99, 0.44 mmol) and an aldehyde (0.4 mmol) was slowly added to this solution over a period of 3 h, and the mixture stirred for a further 2 h. After work-up the aldol adduct was isolated as the corresponding trimethylsilyl ether. Most probably the catalytic cycle is that shown in Scheme 9.30. 

Experimental Procedure 2.1.1. Preparation of a Chromium Carbene Complex from Chromium Hexaearbonyl [Methoxy(methyl)carbene]pentacarbonylchro-mium [37, p 130]... 

Experimental Procedure 2.2.1. Photolysis of a Chromium Carbene Complex 2-Benzyl-4-benzyloxy-4-methyl-2,3,4,4a,7,7a-hexahydro-li/-cyclopenta[c]pyri-din-3-one [294]... 

Experimental Procedure 2.2.6. Cyclopentannulation with a Molybdenum Aryl-carbene Complex 3-Hexyl-5-methyl-l-indanone 346]... 

Experimental Procedure 2.2.7. Diels-Alder Reaction of a Tungsten Vinylcarbene Complex Methyl 2-(2-Furyl)-5-methyl-4-oxo-l-cyclohexanecarboxylate [237]... 

Experimental Procedure 2.2.8. [4 + 3] Cycloaddition of a Chromium Vinylcarbene Complex to a 1-Azadiene rranj-i-(2-Furyl)-2-inethoxy-5-methyl-4,5-dihydro-3H-azepine [390]... 

Experimental Procedure 3.1.1. Preparation of a Molybdenum Carbene Complex by Nucleophilic Abstraction (2,6-Piisopropylphenylimido)bis[ 1,1 -bis(trifluoro-methyl)ethoxy](2-methyl-2-phenyH-propylidene)molybdenum [37,416,417]... 

Experimental Procedure 3.2.6. Alkylidenation of a Ketone 4-Methyl-1-phenyl-octa-1,3-diene [633]... 

Experimental Procedure 4.1.1. Preparation of an Enantiomerically Pure Rho-dium(II) Gomplex Dirhodium(II) Tetrakis[methyl 2-oxo-l-(3-phenylpr( anoyl)-4(S)-imidazolidinecarboxylate] Rh2(4S-MPPIM)4(MeCN)2 [1000]... 

Experimental Procedure 4.2.2. Preparation of an Indole by Intramolecular C-H Insertion Methyl (2S)-2-(3-Acetyl-2-hydroxy-5-aito-lff-l-indolyl)-3-phenylpropanoate [1083]... 

Experimental Procedure 4.2.4. Etherification of a Serine Derivative by Intermo-lecular O-H Insertion Methyl (25)-3-[(Ethoxycarbonyl)methoxy]-2-(benzyloxy-carbonylamino)propanoate... 

Experimental Procedure 4.2.11. Cycloaddition of an Acylcarbene Complex to an Alkyne Ethyl 2-Methyl-5-phenyl-3-furoate [1431]... 

Experimental Procedure 4.2.5. Ammonium Ylide Formation and Stevens Rearrangement Diethyl 2-Benzy 1-2- [(ethoxycarbonyl)methy 1] (methyl)amino malo-nate... 

The technically most important polysulfide is poly thiophenylene or poly(p-phe-nylene sulfide), PPS. It is obtained by reacting sodium sulfide and p-dichlo-robenzene in a polar solvent, for example, l-methyl-2-pyrrolidone at about 280 °C under pressure. The mechanism of the reaction is very complex and cannot be described by a simple aromatic substitution. This synthesis requires special autoclaves and is therefore not suitable for a laboratory course (for an experimental procedure see Table 2.3). 

To better compare modern protocols for the Reformatsky reactions, hereinafter discussed in this section, it is interesting to read, as an example, the experimental procedure reported by R. B. Woodward and coworkers in 1956 for the synthesis of the Lysergic acid precursor 3 (equation 2)14. The procedure adopted was a Barbier-like protocol, involving the addition of Zn and of methyl bromoacetate (la) in three portions to a solution of 2 in hot benzene. 

A significant decrease in reactivity was observed when the IV-aryl zinc enamide generated from 4-methylaniline was used. It was suggested that this 2-methyl effect on reactivity may arise from a steric effect contributing to the conformational stabilization of the transition state. These recent results have thus greatly expanded the scope of the so-called olefinic aldol condensation as the experimental procedure is quite simple and applicable to a variety of monosubstituted or aqa-disubstituted alkenes. 

Typical Experimental Procedure (Scale Up). The following procedure was followed for the large-scale preparation of 99 Solutions of N-(tert-butoxycarbonyl)-D-prolinal (0.1 M, 10 ml in MeOH), l-(2-pyrimidyl) piperazine (0.1 M, 10 ml in MeOH), methyl isocyanoacetate (0.1 M,... 

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