Synthesis alkane elimination

The method of alkane elimination is a versatile approach for the synthesis of inorganic heterocycles comprised of alternating electropositive and electronegative p-block elements. Typically, this method involves the reaction of a homoleptic alkyl derivative of the more electropositive element with a hydride of the more electronegative element with the elimination of a volatile alkane. 

Scheme 2.6 Synthesis of saturated and unsaturated group 13-group 15 heterocycles by alkane elimination.

Specific examples of the application alkane elimination for the synthesis of either saturated or unsaturated group 13-group 15 ring systems are shown in Scheme 2.6 (for a more detailed discussion, see Sections 9.4.1 and 9.4.2). 

Mono(cyclooctatetraenyl) lanthanide(III) compounds, synthesis and characteristics, 4, 124 Mono(cyclooctatetraenyl) zirconium(III) compounds, preparation and reactions, 4, 743 Mono(cyclopentadienyl) amido complexes alkane elimination, 4, 446 amine elimination, 4, 442 HCL elimination, 4, 446 metathesis reactions, 4, 438 miscellaneous reactions, 4, 448 properties, 4, 437... 

Preparation. The synthesis of alkylzinc alkoxides and aryloxides is achieved by an alkane elimination process in the simple reaction of a dialkylzinc compound, R2Zn, with one equivalent of an alcohol, R OH (equation 18). This reaction proceeds either in hydrocarbon solvents or neat solution, to give essentially quantitative yields of the desired products. The volatility of the RH side product helps to drive the equilibrium to the right. The formation of relatively strong Zn-O and C-H bonds, at the expense of breaking the O-H and a relatively weak Zn-C bond also guarantee favorable reaction energetics. 

The most convenient method for the synthesis of lanthanide dialkyl complexes is the alkane elimination reaction of lanthanide trialkyl complexes with a monoanionic preligand (L H) (Equation 8.15). The monoanionic preligands, which have tunable steric and electronic features, are favored for modifying the stability and reactivity of the complexes. Various bulky substituted cyclopentadienyl [4] and non-cyclopentadienyl derivatives have been used as the spectator ligands. The most common types of monoanionic non-cyclopentadienyl ancillary ligands are summarized in Figure 8.10 [36 8]. 

The absence of suitable hydrogen atoms attached to carbon normally prevents the synthesis of R MR molecules by alkane elimination. However, several examples are known. Trimethylindium or [Me2lnNMej]2, formed from Mejin and HNMej reacts with freshly distilled cyclopentadiene at RT in hydrocarbon solvent to precipitate MejInCjHs-h after 48 h in > 70% yield ... 

Dimetallic elimination reactions leading to metal-metal bond formation are the amine or alkane eliminations that result from the condensation of a late transition metal hydrido complex with an early transition metal amido or alkyl complex, respectively. Examples of this method are Selegue s synthesis of the first Ti-Fe and Ti-Ru complexes 8a,b [8, 9] and the reaction of [Zr(CH2Ph)4) with [CoH(CO)4], although only spectroscopic evidence was provided for compound 18 (Scheme 4.3) [20]. 

Dehydrogenation of alkanes is not a practical laboratory synthesis for the vast majority of alkenes The principal methods by which alkenes are prepared m the labo ratory are two other (3 eliminations the dehydration of alcohols and the dehydrohalo genation of alkyl halides A discussion of these two methods makes up the remainder of this chapter... 

Scheme 4. Synthesis of ME-heterocycles by standard hydrogen, alkane and salt elimination...

Several general pathways for the synthesis of group 13/15-heterocycles of the type [R2MER 2]X have been developed over the years. The most important are alkane, hydrogen and salt elimination reactions, as summarized in Scheme 4. 

The synthesis of heterocyclic group 13/15 compounds of the type [R2MER 2]jc has been investigated for many years [21]. General synthetic pathways such as dihydrogen, alkane and salt elimination reactions as summarized in Scheme 3... 

The addition of aluminum during the synthesis of TS-1 reduces its activity for n-octane oxidation. The presence of sodium in the synthesis gel of TS-1 completely eliminates the catalytic activity for alkane oxidation. However, the presence of sodium in preformed TS-1 does not have a significant effect on its catalytic activity. 

Although of relatively weak acidity, amines will react with either carbanionic metal alkyls or hydridic metal hydrides to form amides with the elimination of alkane or hydrogen, respectively. The easiest and most exploited method for the synthesis of lithium and magnesium amides is to treat lithium alkyls or Grignard reagents (normally commercially available) with the corresponding amine (equations 25,47 264 and 2749). 

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