Reaction of benzyl halides

Section 11 14 Benzylic carbocations are intermediates in SnI reactions of benzylic halides and are stabilized by electron delocalization... 

The homo-coupling reaction of benzylic halides by metallic nickel proceeded at room temperature. 1,2-Diarylethanes having a variety of functional groups could be easily prepared by this method in good to high yields. 

The cross-coupling reactions of benzylic halides and acyl halides produced the expected ketones in good to high yields(39,47). The present method can supplement the corresponding Grignard reaction, which does not work well since benzylmagnesium halides undergo dimerization readily. 

Tab. 5.3 Reaction of benzyl halides with hexanoic acid under MW + PTC conditions (10 min, 560 W, 10% PhCH2N+Me3Cr).

When sodium ethoxide is used in place of sodium hydroxide in the carbonylation reaction of benzyl halides with dicobalt octacarbonyl, ethyl esters are produced instead of the acids [15], Esters are also produced directly from iodoalkanes through their reaction with molybdenum hexacarbonyl in the presence of tetra-/i-butylammo-nium fluoride [16]. Di-iodoalkanes produce lactones [16]. The reaction can be made catalytic in the hexacarbonyl by the addition of methyl formate [16]. t-Butyl arylacetic esters are produced in moderate yield (40-60%) under phase-transfer catalytic conditions in the palladium promoted carbonylation reaction with benzyl chlorides [17]. 

Reactivities comparable to allylic halides are found in the nucleophilic displacement reactions of benzylic halides by SN1 and SN2 mechanisms (Table 14-6). The ability of the benzylic halides to undergo SK1 reactions clearly is related to the stability of the resulting benzylic cations, the electrons of which are extensively delocalized. Thus, for phenylmethyl chloride,... 

Hass, H. B. Bender, M. L. The reaction of benzyl halides with the sodium salt of 2-nitro-propane. A general synthesis of substituted benzaldehydes./. Am. Chem. Soc. 1949, 71, 1767-1769. 

Aromatic halides are reported to give only carbonylated products with nickel tetracarbonyl. In contrast, pentafluorophenyl iodide in DMF gives decafluorobiphenyl in 70% yield (27). From the other products obtained (pentafluorobenzene, decafluorobenzophenone) it has been suggested that a radical mechanism is involved. The reactions of benzyl halides with nickel carbonyl in various solvents have been reported (28). The main reaction involves carbonylation, as discussed in Section III. Using benzene as solvent, a 33% yield of bibenzyl may be obtained. Here again a mechanism involving a 7r-allylnickel derivative should perhaps be considered, particularly since such a system is known to exist in (XVI) (29). 

The nucleophilic photosubstitution reactions of benzylic halides with a nitro group at the ortho- or / ara-position of the aromatic ring such as / -nitrocumyl chloride (26) occur via the S l mechanism. The reactions have been reviewed in References 6-10. The initiation and propagation steps of this photoinduced radical-chain electron transfer process have already been depicted in this review in equations 6 to 9 in Section II. A. Equation 37... 

SN 2 reactions of benzyl halides efficiently convert aromatic methyl groups to functional groups. Halogenation, followed by substitution, gives the functionalized product. 

Pettier LR, Peyrat JF, Alami M, Brion JD (2004) Unexpected tandem sonogashira-carbo-palladation-sonogashira coupling reaction of benzyl halides with terminal alkynes a novel four-component domino sequence to highly substituted enynes. Synlett 1503-1508... 

Apart from carbonylation reactions of benzyl halides, similar reactions using aryl halides have attracted industrial interest. Among the carbonylation reactions of aryl halides, those of heteroaryl halides were of special interest to industrial research groups. The attachment of carbonyl functionalities onto heterocyclic frameworks by replacing a halide substituent provides an easy access to valuable intermediates for the manufacture of herbicides and pharmaceuticals (e. g., Diflufeni-can, Imazapyr, Nicosulfuron, Isoniazid, Etofibrat, Nifluminacid [55]). 

Another synthesis of isoquinolines in which two ring bonds are formed involves the reaction of benzyl halides (74) with the sodium salt of N-(tosylamino)acetaldehyde dimethyl acetal. Treatment of the intermediate (75) with hydrochloric acid results both in ring-closure and aromatization (Scheme 48). ... 

Barbier reaction. A catalytic amount of AgN03 is important in the Zn-mediated reaction of benzylic halides with ArCHO in buffer solutions (pH 12) as less bibenzyls are formed. 

As with preparing allyl complexes, direct reaction of benzyl halides and alkali metals is not a generally useful route to benzylalkali metal compounds due to R-R coupling. Benzylalkali metal compounds can be prepared by (1) addition of organometallic reagents to arylalkenes, (2) cleavage of benzyl ethers (equation 28), (3) transmetallation (equations 29-31), and (4) metallation of methyl substituted aromatics. Q, Q -Bis(trimethylsilyl)benzyl potassium can be prepared by metallation with a mixture of butyllithium and potassium 3-methyl-3-pentanolate in THF. ... 

S l reactions of benzylic halides proceed at rates faster than those of simple alkyl halides. 

At first glance it may not seem important to calculate NBMOs for odd alternant systems. Most stable molecules have an even number of n centers, and the method presented here allows us to determine only one of several molecular orbitals. Nevertheless, the method is very valuable because odd alternant systems may be important intermediates in chemical reactions, and the properties of the NBMO are vital to their reactions. For example, the benzyl radical is an intermediate in the a-halogenation of toluene, and benzyl carbocations are intermediates in SnI reactions of benzyl halides. Therefore, calculating properties of these systems can give useful information about chemical reactions. 

Hu, Y.-m., Zhou, J., Long, X.-t. et al. (2(X)3) Palladium-catalyzed cascade reactions of benzyl halides with A-allyl-A-(2-butenyl)-p-toluenesulfonamide. Tetrahedron Lett., 44, 5009-10. 

The reactions of benzylic halides with carbon monoxide and alcohols form esters in good yields. However, the reactions of alkyl halides are more limited for two reasons. First, the oxidative addition of alkyl halides occurs less readily to palladium complexes than the oxidative addition of aryl halides. This difference was noted in Chapter 7. Second, the intermediate alkylpalladium halide can undergo P-hydrogen elimination. As noted in Chapters 9 and 10, these hurdles have been overcome in some cases, and cross-coupling... 

Disulphides have been obtained by the solid state reaction of benzyl halides, alkyl halides and acyl halides at room temperature in the presence of benzyltriethylammonium tetrathiomolybdate. For example, butyl iodide, benzyl bromide and benzoyl chloride give the corresponding disulphides in 70-74%... 

Preparation of 3-Arylpropanenitriles by Nickel-Mediated Reaction of Benzylic Halides with Haloacetonitriles... 

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