Alkylation with allylic halide

Allyl sulphones can be converted to dienes by alkylation and elimination of sulphinic acid under basic conditions (equation 64)105. Several vitamin A related polyenes have been synthesized following this two-step protocol (Table 10)106. The poor leaving-group ability of the arylsulphonyl group requires treatment with strong base for elimination. However, elimination of the allylsulphonyl group takes place readily under palladium catalysis (equation 65)107. Vinyl sulphones can be converted to dienes via Michael addition, alkylation with allyl halides and elimination of sulphinic acid sequence (equation 66)108. 

Amino acid synthesis (8, 389). Alkylation of the aldimine (1) from glycine ethyl ester and /j-chlorobenzaldehyde under phase-transfer conditions offers a general route to amino acids. Either liquid-liquid phase-transfer or solid-liquid phase-transfer catalytic conditions are satisfactory with active halides, but alkylation with allylic halides and less active alkyl halides is best effected under ion-pair extraction conditions (6,41), with 1 equiv. of tetra-n-butylammonium hydrogen sulfate (76-95% yields).1... 

Alkylation with allyl halides gives olejinic amines ... 

The addition of copper iodide to (61f), followed by alkylation with allylic halides, gives y-allylation products with inversion of the allyl unit, whereas reaction with acetone yields predominantly the a-ad-... 

Copper dienolates of a,/3-unsaturated acids, prepared by Copper(I) Iodide transmetalation, can be selectively y-alkylated with allylic halides the use of nonallylic electrophiles leads mainly to a-alkylation (eq 20). Copper enolates of a,fi-unsaturated esters and amides show similar behavior. 

In further studies, Chou and colleagues found that the sulfolene nucleus could be regioselectively substituted with alkyl chains incorporating an alkene bond. Alkylations with allylic halides were particularly effective (Scheme 6.25, Table 6.8). They utilized this chemistry in neat syntheses of simple terpenes (see Section 6.4). In some cases the alkene bond of the side-chain was utilized as a dienophile in an intramolecular Diels-Alder reaction [43,46,69,109]. 

Scheme 12.37 Allylic alkylations with allyl halides [71].

Alkylations with Allyl Halides. The enhanced reactivity of allyl halides is reflected in the reactions of both (1) and (3). Thus (1) reacts with 2-f-butylsulfonylallyl bromide at low temperatures (eq 6). ... 

A fundamental problem in the alkylation of enamines, which is inherent in the bidentate system, is the competition between the desired carbon alkylation and attack at the nitrogen. With unactivated alkyl halides (3,267), this becomes especially serious with the enamines derived fromcycloheptan-one, cyclooctanone, cyclononanone, and enamines derived from aldehydes. Increasing amounts of carbon alkylation are found with the more reactive allyl and benzyl halides (268-273). However, with allyl halides one also observes increasing amounts of dialkylation of enamines. 

Symmetrical thioethers can also be prepared by treatment of an alkyl halide with sodium sulfide, or with S(MgBr)2 with allylic halides. ... 

The next stage in the route to a-kainic acid was the alkylation of (5) with allylic halide (9). Even in... 

Alkylation by allylic halides is usually a satisfactory reaction, and in this case the reaction may proceed through a cyclic mechanism.81 For example, when l-14C-allyl chloride reacts with phenyllithium, about three-fourths of the product has the labeled carbon at the terminal methylene group. 

The benzotriazole 109 reacts with alkyl or allyl halides in the presence of bismuth(III) chloride and metallic aluminium to give the homoalkylated amines 110 in high yields119. 

The reaction of methylenesulphones with allyl halides in the presence of quaternary ammonium salts produces the 1-allyl derivatives [52], unlike the corresponding reaction in the absence of the catalyst in which the SN- product is formed (Scheme 6.5). In contrast, alkylation of resonance stabilized anions derived from allyl sulphones produces complex mixtures [51] (Scheme 6.6). Encumbered allyl sulphones (e.g. 2-methylprop-2-enyl sulphones) tend to give the normal monoalkyl-ated products. Methylene groups, which are activated by two benzenesulphonyl substituents, are readily monoalkylated hydride reduction leads to the dithioacetal and subsequent hydrolysis affords the aldehyde [61]. 

Alkylation of enamines may lead to the formation of N-alkylated product, which on heating is converted to C-alkyl compound (This rearrangement is common with allylic halide, alkyl halide or a-haloacetic ester. 

Zinc homoenolate reacts with allylic halides and diene monoepoxides under copper catalysis [29]. Treatment of the zinc nomoenolate with a catalytic amount of Cu(II) in a polar solvent (e.g. hexamethylphosphoramide, HMPA, N,N-dimethylacetamide, DMA) generates a copper species which undergoes clean Sn2 allylation reactions Eq. (40). Polar solvents not only accelerate the reaction but greatly improve the SN2 selectivity. A variety of allylating reagents can be employed in this reaction (Table 9). The SN2 /SN2 ratio is particularly high (close to 100%) when the alkylated carbon bears no substituents. The reaction of... 

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