Zinc reagents properties

These zinc reagents provide a useful entry into compounds containing the dialkoxyphosphinyldifluoromethyl group.36 Introduction of this moiety into organic molecules has attracted attention due to biological properties exhibited by these derivatives as compared to their non-fluorinated analogues.37... 

The alkyl transfer properties of dialkyl zinc reagents have been studied in the reaction of Zn[CH(SiMe3>2]2 with TiCU- The monoalkyl trichloro titanium complex TiCl3[CH(SiMe3)2] was obtained in 83% yield.10... 

Carbonates, like esters, can be cleaved by basic hydrolysis, but generally are much less susceptible to hydrolysis because of the resonance effect of the second oxygen. In general, carbonates are cleaved by taking advantage of the properties of the second alkyl substituent (e.g., zinc reduction of the 2,2,2-trichloroethyl carbonate). The reagents used to introduce the carbonate onto alcohols react readily with amines as well. As expected, basic hydrolysis of the resulting carbamate is considerably more difficult than basic hydrolysis of a carbonate. 

However, lithinm aluminum hydride or zinc metal and HCl (5) are required as reducing agents to reduce the thiocyanate to the thiol. These reducing agents are stoichiometric reagents and aren t environmentally acceptable at this time because of their hazardous properties and waste disposal problems on a large manufacturing scale. 

Catalytic properties of external chiral additives such as (2S,3/ )-4-dimethyl-amino-l,2-diphenyl-3- methyl-2-butoxide (A 16) (574, 575) and 2-magnesium-3-zinc salts of dialkyl (f ,f )-tartrate (A17) were employed in the highly stereoselective addition of organozinc reagents to derivatives of 3,4-dihydro-isoquinoline-A-oxide (Scheme 2.147) (576). 

Jiang Hao, Hu Yuehua, Xu Jing, 2000. Electrochemical characteristics of couple electrode of galena-pyrite in different solutions. Trans. Nonferrous Met. Soc. China, 10 87 - 88 Johnson, N. W. and Munro, P. D., 1988. h-pH measurements for problem solving in a zinc reverse flotation process. Austral Inst. Min. Metall., 239(3) 53 - 58 Karkovsky, I. A., 1957. Physicochemical properties of some flotation reagents and their salts with ions of heavy iron-ferrous metals. Proc. 2nd Int. Congr. Surface Activity, London, 4 225 - 237... 

The second major advantage of this method is that a wide range of new cyclopropanating reagents with new properties became available. If a sufficiently acidic compound reacts with diethylzinc, a mixed zinc species is formed (equation 5). The second ethyl group can then be exchanged with an iodomethyl unit to generate a potentially reactive iodomethylzinc species. 

The synthesis of functionalized zinc organometallics can be accomplished with a variety of methods that have been developed in recent years. The intrinsic moderate reactivity of organozinc reagents can be dramatically increased by the use of the appropriate transition metal catalyst or Lewis acid. Furthermore, the low ionic character of the carbon-zinc bond allows the preparation of a variety of chiral zinc organometallics with synthetically useful configurational stability. These properties make organozinc compounds ideal inteimediates for the synthesis of complex and polyfunctionalized organic molecules. 

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