Grignard reagents/zinc chloride

KETONES Bis(phenylthio)methane. Chlorothexylborane. Grignard reagents. Nickel chloride-Zinc. o-Nitrophenyl selenocyanate. Organomagnesium(II) iodides. PhcnylthiophenyKtrimethyl-silyDmcthanc. 

After discovery of the higher stereoselectivities made possible by the zinc chloride catalysis, the synthesis was applied to several secondary alcohols having two or more stereocenters15. The first of these (35,4S)-4-methyl-3-heptanol, was first made with (S)-pinanediol as the chiral director, but has since been made more stereoselectively with (R,R)-2,5-dimethyl-3,4-hexanedi-ol (Section 1.1,2.1.2.1.). Another insect pheromone, eldanolide, requires the use of (R)-pinane-diol in order to obtain the natural enantiomer, and introduces the use of an enolate as well as an allylic Grignard reagent for C-C bond formation15. 

Grignard reagents and diazonium zinc chloride double salts have been used to prepare azo compounds. The reaction of arylzinc chloride with a diazonium salt has also been used. By this means, mixed aromatic-aliphatic azo compounds have been prepared. 

SPIROI.ACTONF.S Allyltrimethylsilyl-zinc chloride. Grignard reagents. 

Arylzinc halides, and zinc dialkyls and di-aryls may be prepay by the action of the Grignard reagent on anhydrous zinc chloride in ether solution.6... 

As shown in Scheme 78, with or without zinc chloride, benzylic Grignard reagents couple with vinyl bromide to form allylbenzene derivatives in high ee (188). This method has been used to prepare optically active allylsilanes in up to 95% ee. Vinylic bromides with E configurations lead to the E allylsilanes with high ee, and Z bromides lead to Z allylsilanes with lower ee. 

Feringa reports that alkyl heterozincates (131), made from zinc chloride-TMEDA complex, potassium f-butoxide and alkyl Grignard reagents in ether (or tetrahydrofuran), are highly effective in 1,4-additions to ot,P-enones (>85%) while the aryl heterozincates are less efficient (<50%).106... 

Compared with asymmetric ethylation, reports on asymmetric phenylation are limited. We disclosed the enantioselective phenylation using diphenylzinc prepared in situ from phenyl Grignard reagent and zinc chloride. This method needs a stoichiometric amount of chiral amino alcohol DBNE 18 but good ee of 82% was achieved [32], A catalytic phenylation was examined using planar chiral compound 1 based on ferrocene, and chiral diaryl carbinols of moderate ee were provided from diphenylzinc and 4-chlorobenzaldehyde (Scheme 10) [33]. A catalytic and highly enantioselective phenylation was realized by binaphthyl-based chiral catalyst 23. In this reaction, the addition of 2 equivalents of diethyl-zinc against catalyst increases the yield and ee [34]. Recently, chiral amino alcohol DPMPM 9 was also reported to be an efficient catalyst for asymmetric phenylation [35]. 

Chloro diamido complexes, with Ti(IV), 4, 418 419 Chlorodi- -butyltin hydride, in hydrostannations, 9, 351 Chlorodienes, and Grignard reagent reactivity, 9, 51 l-Chloro-2,2-difluorovinylzinc chloride, via lithium—zinc... 

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