Metal nitriles

TABLE 9. Preparation of cyclopropanes 111 from a,/ -unsaturated sulfones 109 and a-metallated nitriles 11071... 

Not only alkenes and arenes but also other types of electron-rich compound can be oxidized by oxygen. Most organometallic reagents react with air, whereby either alkanes are formed by dimerization of the metal-bound alkyl groups (cuprates often react this way [80]) or peroxides or alcohols are formed [81, 82]. The alcohols result from disproportionation or reduction of the peroxides. Similarly, enolates, metalated nitriles, phenolates, enamines, and related compounds with nucleophilic carbon can react with oxygen by intermediate formation of carbon-centered radicals to yield dimers (Section 5.4.6 [83, 84]), peroxides, or alcohols. The oxidation of many organic compounds by air will, therefore, often proceed faster in the presence of bases (Scheme 3.21). 

The photolytic rearrangement of metal nitrile imines 31 also affords P-substituted carbodiimides 32 ... 

Similarly, the nucleophilic substitution at sulfur in [(—)-menthyl] (A)-4-methylbenzenesul-finate by prostereogenic a-metalated nitriles yields the corresponding a-cyano sulfoxides 3 as diastereomeric mixtures. On oxidation these are converted to the corresponding sulfones with a stereogenic center at the a-carbon atom only73. 

In another study, the metal-induced self-assembly of other cage stuctures, in which four platinum(II) or palladium(II) ions serve to link two preorganised (identical) cone-shaped precursors via cis nitrile-metal-nitrile bonds, has been reported. 

The Ru(NH3)2 + group has remarkable 7t-bonding properties, which are shown, not only by the formation of N2, CO and similar complexes, but also by the fact that in nitrile complexes, [Ru(NH3)5NCR]2+, the CNstretching frequency is substantially lower than in the free nitrile, whereas in other metal nitrile complexes, even in [Runl(NH3)5NCR]3+, the frequency is invariably higher.17... 

In some cases this further reaction can be suppressed by adding the sulfenylating agent (preferably in excess) in one portion, but a more successful procedure involves addition of RR CHM to a solution of a (100%) excess of R"SSR". If the disulfide is non-volatile (PhSSPh ) and hence the excess is difficult to remove from the product mixture, this procedure is not attractive. Especially in the cases of metallated nitriles RCH2C=N and ketone enolates the further sulfenylation is a problem which has not yet been satisfactorily solved. 

Alkylation of Metallated Nitriles in Liquid Ammonia and in Organic Solvents... 

Disubstitution is not observed in reactions of metallated nitriles with epoxides and with aldehydes and ketones. 

Compared with other synthetic intermediates, enolates show a decreased reactivity. The differences in reactivity are most striking in reactions with alkylating agents [1] and epoxides [6]. The reactivities of the various types of enolates towards alkyl halides decrease in the order C=C(0 )NR2 (amide-enolate) C=C(0 )0R (ester enolate) C=CO (ketone-enolate). Metallated nitriles, imines, and S,S-acetals are, in general, much better nucleophiles than enolates in alkylations and ft-hydroxyalkylations [1], Furthermore, the alkylation of aldehyde and ketone enolates usually does not stop after the mono-functionalization [12]. The decreased reactivity of (especially) aldehyde and ketone enolates also appears in thiolations with disulfides [2]. A solution of lithiated cyclohexanone in THF does not react at 20°C with CH3SSCH3 [1,2]. 

Protonation of the product of this reaction (pi Ta 3.02) occurs at the carbonyl oxygen atom rather than at the NH group. Data are also reported for the base hydrolysis of benzonitriles in complex ions of the type [Co(NH3)6(NCC8H4R)] + (R = 4-CN, 3-CN, 4-Ac, 3-CHO, or 4-CHO). The results of these studies are compared with analogous results for other metal nitriles in Table 20. Ruthenium(m) is seen to be most effective in catalysing the base hydrolysis of acetonitrile, and this is attributed... 

The cyclization reactions of dideuterated hydroxynitrile (10) with n-BuLi forming the Af-metalated nitrile, or with i-PrMgCl giving the C-metalated nitrile, that form trans- and cis-decalin, respectively. Scheme 11, have shown that both reactions occur exclusively by an 5 mechanism. In fact, this mechanism is found for all the cyclizations of primary allylic chlorides. Secondary and trisubstituted allylic chlorides also react with n-BuLi or j-PrMgCl giving either the trans- and c -decalin by an 5 or an mechanism. Yields for the cyclization range from 34 to 89%. 

A full account has been given of the preparation of cyclopropylmethanols or cyclobutanols from y-epoxysulphones (Scheme 1). This useful method can also be applied to the synthesis of cyclopentanols from 5-epoxysulphones. The same idea has been used by Gaoni in a simple synthesis of bicyclo[1.1.0]butanes (6). a,j8-Unsaturated sulphones (7) undergo Michael attack by a-metallated nitriles leading to the cyclopropanes (8) as yet the method is limited to cases where R = Phor SR ... 

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