Zinc dichloride

In particular 1- or 3-hetero-substituted allylzinc reagents are often prepared in situ by adding anhydrous zinc dichloride or dibromide to the solution of the allyllithium compound. 

A number of zinc-bound bidentate bis(thioether) donor ligands were characterized as distorted tetrahedral complexes of zinc dichloride. The complexes 2,3-bis(methylthio)hexane,l,2-bis (methylthio) cyclohexane, and m-[5,6-bis(methylthio)-l,3-cycloheptadiene showed a variation in S—Zn—S angles.539... 

The molecular structures from electron diffraction of zinc dichloride, zinc dibromide, and zinc diiodide have been reinvestigated.612 The important effects halides have on geometry have also been investigated, in particular the changes from octahedral to tetrahedral geometry in the presence of chloride ions have been studied.613... 

Treatment of zinc dichloride with various 1,4-dilithiobutanes gave the corresponding contact ion pair dilithio bis(l,4-dibutanediyl)zincates as ether and TMEDA adducts.123 Figure 35 shows the solid-state structure of the... 

Brimble and coworkers172 reported the asymmetric Diels-Alder reactions between quinones 265 bearing a menthol chiral auxiliary and cyclopentadiene (equation 73). When zinc dichloride or zinc dibromide was employed as the Lewis acid catalyst, the reaction proceeded with complete endo selectivity, but with only moderate diastereofacial selectivity affording 3 1 and 2 1 mixtures of 266 and 267 (dominant diastereomer unknown), respectively. The use of stronger Lewis acids, such as titanium tetrachloride, led to the formation of fragmentation products. Due to the inseparability of the two diastereomeric adducts, it proved impossible to determine which one had been formed in excess. 

Brimble and coworkers176 studied the asymmetric Diels-Alder reactions of cyclopentadiene with chiral naphthoquinones 272 bearing different chiral auxiliaries. The highest endo and facial selectivities were obtained using zinc dichloride as the Lewis acid catalyst and (—)-pantolactone as the chiral auxiliary. Thus, the reaction between cyclopentadiene and 272 afforded a 98 2 mixture of 273 and 274 (equation 76). The chiral auxiliary was removed easily by lithium borohydride reduction. 

Synonym Zinc dichloride fame Physical Form. White fame Uses. Smoke generators flax in soldering Exposure. Inhalation... 

With the help of zinc dichloride, dichloride 6 is treated first with methyilithium and then with Z-propeny Ilithium. In the process, 6 reacts at -78 "C initially with methy Ilithium to give at complex 20. which at higher temperature decomposes to the substitution product. The mechanism of the second reaction is analogous. If one interchanges the two synthetic steps what results is an intermediate (a-chlorcrotyl) boron ate, which proves unstable with respect to isomerization of the double bond and epimeri/ation of the stereogenic center in the allylic position.13... 

ZnCl2 is complicated by the formation of trimeric Cu3Cl3 molecules in the liquid and gaseous phases gaseous zinc dichloride is apparently monomeric, and the structure of the liquid phase is uncertain. 

Polycyclic aromatic compounds are obtained upon irradiation of diaryl-substitnted chromium carbenes under a carbon monoxide atmosphere. The reaction probably proceeds via the formation of a biaryl-aUcoxy ketene followed by cyclization. For example, the pyrrole-substituted carbene (22) gave the tricyclic compound (23) (Scheme 34) Related intramolecular Friedel-Crafts-type reactions of carbenes having tethered electron-rich aromatic rings are feasible, usually in moderate yields (Scheme 35). A Lewis acid catalyst such as zinc dichloride is required for optimum yields. 

SYNS BUTTER of ZINC CHLORURE de ZINC (FRENCH) ZINC BUTTER ZINC CHLORIDE (ACGIH, OSHA) ZINC CHLORIDE, anhydrous (UN 2331) (DOT) ZINC CHLORIDE, solution (UN 1840) (DOT) ZINC (CHLORURE de) (FRENCH) ZINC DICHLORIDE ZINC MURIATE, solution (DOT) ZINCO (CLORURO di) (ITALIAN) ZINKCHLORID (GERMAN) ZINKCHLORIDE (DUTCH)... 

Because of the extensive amount of waste generated in traditional Friedel-Crafts reactions, it is not surprising that this reaction has been studied in RTIL. Early examples included the use of catalytic chloroaluminate ionic liquids. However, the moisture sensitivity of such systems was a drawback. Therefore, water-stable rare-earth Lewis acids, such as Sc(CF3S03)3, have come to be used for these reactions.The same Lewis acid has also been used to catalyse Diels-Alder reactions in RTILs.Interestingly, in this example, the RTIL not only provided a means for recycling the catalyst but also accelerated the rate and improved selectivity. It has also been demonstrated that a moisture stable, Lewis acidic, catalytic ionic liquid could be prepared from choline chloride and zinc dichloride, and that this was an excellent medium for the Diels-Alder reaction. Yields of 90% or more were achieved in reaction times of between 8 min and 5h for a range of dienes and dienophiles. 

The following test systems were selected Lewis acids-. Boron trifluoride etherate, titanium tetrachloride, aluminum trichloride, zinc dichloride, and zinc diiodide Amines Benzylamine, butylamine, morpholine, and dipropylamine. The distribution of these items in the corresponding score plots are shown in Fig. 16.7. 

Lewis acids used for acylation of allylsilanes with acid chlorides include titanium and tin tetrachlorides, aluminum, gallium and indium trichlorides and zinc dichloride, and boron trifluoride for reactions with acid anhydrides. Although gallium and indium chlorides have been used successfully in catalytic (ca. 2 mol %) amounts, most frequently aluminum chloride has been used as catalyst, with titanium tetrachloride also commonly employed, both in molar quantities. With these catalysts, acylations can often be carried out at low temperatures, and with short reaction times. 

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