Zinc chloride s. a. under

Mercuric oxide s. under BFg Zinc chloride (s. a. under RgSiH) 4-Thiazoline-2-thiones from dithiourethans... 

Sodium acetate s. under (CHgC0)20 Triethylamine s. under CgH NCO and COCI2 Pyridine s. under RN C NR, POClg, and TsCl Mercuric oxide s. under BFg Zinc chloride (s. a. under ZnCl2)... 

Zinc chloride s. under R SiH Lithium tetrahydridoborate a-Hydroxymethyl-a-aminocarboxylic aeids from a-acetamino-a-cyanocarboxylic acid esters... 

Zinc chloride s. under CI2CHOCH3 Dimethijlformamide s. under SOCI2 a,a-Dichloromethyl ether/zinc chloride Sulfonic acid chlorides from sulfonic acids... 

The manufacture of crystal violet (1), however, is a special case which does not involve the isolation of the intermediate Michler s ketone (Fig. 3). Thus, phosgene is treated with excess dimethyl aniline in the presence of zinc chloride. Under these conditions, the highly reactive intermediate "ketone dichloride" is formed in good yield this intermediate further condenses with another mole of dimethyl aniline to give the dye. 

Ion 21 can either lose a proton or combine with chloride ion. If it loses a proton, the product is an unsaturated ketone the mechanism is similar to the tetrahedral mechanism of Chapter 10, but with the charges reversed. If it combines with chloride, the product is a 3-halo ketone, which can be isolated, so that the result is addition to the double bond (see 15-45). On the other hand, the p-halo ketone may, under the conditions of the reaction, lose HCl to give the unsaturated ketone, this time by an addition-elimination mechanism. In the case of unsymmetrical alkenes, the attacking ion prefers the position at which there are more hydrogens, following Markovnikov s rule (p. 984). Anhydrides and carboxylic acids (the latter with a proton acid such as anhydrous HF, H2SO4, or polyphosphoric acid as a catalyst) are sometimes used instead of acyl halides. With some substrates and catalysts double-bond migrations are occasionally encountered so that, for example, when 1 -methylcyclohexene was acylated with acetic anhydride and zinc chloride, the major product was 6-acetyl-1-methylcyclohexene. ... 

Y Picoline. Commercially pure y-picoline contains )S-picoline and 2 6-lutidine and sometimes traces of non-basic impurities (aromatic hydrocarbons) which cannot be separated by fractionation. The non-basic impurities are removed by steam distillation of the base in dilute hydrochloric or sulphuric acid solution (for details, see under a Picoline). The impure y-picoline is converted into the zinc chloride complexes of the component bases the 2 6-lutidine - ZnClj complex is the least stable and upon steam distillation of the mixture of addition compounds suspended in water, 2 6-lutidine passes over flrst. The complete separation of the 2 6-lutidine may be detected by a determination of the density and the refractive index of the dry recovered base at varioiu stages of the steam distillation. The physical properties are —... 

Several techniques have been used to activate the zinc metal and improve yields. For example, pretreatment of zinc dust with a solution of copper acetate gives a more reactive zinc-copper couple.168 Exposure to trimethylsilyl chloride also activates the zinc.169 Wilkinson s catalyst, RhCl(PPh3)3 catalyzes formation of Reformatsky reagents from diethylzinc, and reaction occurs under very mild conditions.170... 

Under the influence of zinc chloride, Danishefsky s diene 4 reacts with simple imines to give dihydro-y-pyridones 100 (e.g. R1 = n-Bu, Ph, Bn R2 = Pr, i-Pr, Ph) in 62-76% yields (equation 58)51. In contrast, the Et2AlCl-catalyzed reaction of the diene 86 with benzylidenemethylamine (101) results in the formation of the dihydro-a-pyridone 102 (equation 59)52. 

Mercaptolysis of /3-D-glucopyranose pentaacetate in ethyl mercaptan at 0°, with zinc chloride as catalyst, gives ethyl tetra-O-acetyl-l-deoxy-1-thio-/S-D-glucopyranoside in 71% yield. Under the same conditions, a-D-glucopyranose pentaacetate reacted only very slowly, but it could be shown that the deoxy-thio-/3-D-glucoside is formed in much greater amount than is the a anomer. Mercaptolysis of the D-mannopyranose pentaacetates under the same conditions for 48 hours resulted in a 70% yield of ethyl tetra-O-acetyl-l-deoxy-l-thio-a-D-mannopyranoside from the /3-D-pentaacetate, and in a 60% yield from the a anomer.103 Inspection, by preparative paper chromatography, of the residual sirups, after deacetylation, led in each case to the isolation of the anomeric ethyl-1-... 

Since Hausmanrfs and Kipping s initial studies, the synthesis of truxene from 1-indanone has been carried out many times under a wide variety of conditions. Reagents that have been reported to promote this trimerization are generally either strong protic acids or Lewis acids and include hydrochloric acid [15], hydroiodic acid [15], phosphorus pentoxide [15], zinc dust [15], sulfuric acid [17], phosphorus pentachloride [17], zinc chloride in acetic acid [18],... 

Efforts to synthesize apoharmine (1, R = Me) by Fischer cyclization of ethyl pyruvate 2-methyl-3-pyridylhydrazone failed, whereas its cyclohexanone hydrazone gave tetrahydroharman (27, R = Me) in 11 % yield on heating with zinc chloride. This yield seems quite low compared to the 94 % yield of a 2 1 mixture of tetrahydro-S-carboline (28) and tetrahydro-j8-carboline (27, R = H), respectively, obtained from cyclohexanone 3-pyridylhydrazone under similar conditions. Okuda and Robison were able to cyclize cyclohexanone 2-pyridyl-hydrazone to 5,6,7,8-tetrahydro-a-carboline in 53 %yield on heating in polyphosphoric acid, but the acetaldehyde, acetone, and pyruvic acid... 

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