Allylic derivatives preparation

In addition to the preparation of l-alkenes, the hydrogenolysis of allylic compounds with formate is used for the protection and deprotection of carboxylic acids, alcohols, and amines as allyl derivatives (see Section 2.9). 

Formation of AllylEsters. AEyl esters are formed by reaction of aEyl chloride with sodium salts of appropriate acids under conditions of controEed pH. Esters of the lower alkanoic, alkenoic, alkanedioic, cycloalkanoic, benzenecarboxyEc, alkylbenzene carboxyEc, and aromatic dicarboxyEc acids maybe prepared in this manner (25). More information can be found about the reactivity of aEyl compounds (see Allyl alcohol and mono allyl derivatives). 

Allylboronates prepared from simple diols display appreciable reactivity, but eyelie boronate derivatives prepared from 1,2- or 1,3-diols display considerably less. The commonly employed pinacol esters are among the least reactive members of this class. 2-Allyl-3-methyl-l,3,2-oxaza-... 

The breakthrough was achieved with the creation of dialkoxy(tj5-cyclopentadienyl)titanium(IV) chlorides derived from sterically hindered chiral alcohols11 35,35a 36. Allyl derivatives 8 and 10, prepared in situ from complexes 7 and 9, have sufficient stability and reactivity. 

Alkyl, aryl, and allyl derivatives of boron can be prepared directly from the corresponding halides, BF3, and magnesium metal. This process presumably involves in situ generation of a Grignard reagent, which then displaces fluoride from boron.2... 

Alkenylbenzotriazoles 865 are readily prepared by isomerization of the corresponding allyl derivatives catalyzed by Bu OK. Lithiated compounds 865 are treated with electrophiles to provide a-substituted derivatives 866. Epoxidation of the double bond with ///-chloroperbenzoic acid converts intermediates 866 into oxiranes 867 that can be hydrolyzed to furnish a-hydroxyketones 868 in good yields (Scheme 140) <1996SC2657>. 

Thermally promoted Claisen rearrangement of simple allyloxypyrimidines is difficult to effect, but is more common with quinazolines where it has been used to prepare allyl derivatives substituted in the carbocyclic ring < 1996HC(55) 1 >. An attempted amino-Claisen rearrangement of a 4-allylaminopyrimidine was unsuccessful <2005AJC368>. 

The A -allyl derivative nalorphine (3-2) is prepared from A -demethylmorphine (3-1) by alkylation with allyl bromide [2]. The discovery that this compound proved to antagonize the activity of morphine in experimental animals led to the synthesis of the potent opioid antagonist naloxone (8-3), which is discussed below. Nalorphine (3-2), in marked contrast to the latter, does show some modest analgesic activity in humans. 

By far the most thoroughly investigated azocines are the 2-methoxy derivatives prepared and studied by Paquette and coworkers (7lAG(E)ll). The synthesis involves addition of chlorosulfonyl isocyanate to a cyclohexadiene, conversion to the imidate and introduction of another double bond by allylic bromination and dehydrohalogenation. Valence isomerization then ensues and 2-methoxyazocine (98) or alkyl homologs are isolated from this sequence in multigram quantities as stable yellow oils. NMR data (see 98) clearly indicate the monocyclic azocine structure the spectra are invariant from -70 to 180 °C and indicate less than 2% of the bicyclic valence isomers. 

Enantiomerically-pure sulfoxides are readily available. Ilan Marek of Technion-Israel Institute of Technology reports (1. Am. Chem. Soc. 125 11776, 2003) that alkyne-derived sulfoxides such as 8 can be used to direct the addition of an allylic organometallic, prepared in situ, to an aldehyde 9. Both the secondary alcohol, from the aldehyde, and the adjacent quaternary center of 10 are formed with >99% stereocontrol. 

The use of mixtures of glycerol and formic acid for the preparation of allyl derivatives (allyl ch oride and allyl formate) has recently been described by Aschan.2 Allyl alcohol has also been isolated from crude wood alcohol.3 A special method for titrating allyl alcohol has been described.4... 

Imidazo[l,5-a][l,3,5]triazinones (191) have been prepared from pyrimidines such as (190) by cleavage of the C(4)-C(5) bond and cyclization to the desired product (Scheme 116) (79JOC1740). The allyl derivative (192) is formed in the same way (equation 112) (81JOC3681). 

The phase-transfer technique of partial alkylation introduced by Garegg in the carbohydrate-field (see Sect. 2.2) can be used also for the preparation of partially allylated derivatives. It was found that the reaction of benzyl 4-0-benzyl-a-L-rhamnopyrano-... 

Cyano compounds liquid crystals, 12, 278 in silver(III) complexes, 2, 241 Cyanocuprates, with copper, 2, 186 Cyano derivatives, a-arylation, 1, 361 Cyanosilanes, applications, 9, 322 Cyclic acetals, and Grignard reagent reactivity, 9, 53 Cyclic alkenes, asymmetric hydrosilylation, 10, 830 Cyclic alkynes, strained, with platinum, 8, 644 Cyclic allyl boronates, preparation, 9, 196 Cyclic allylic esters, alkylation, 11, 91 Cyclic amides, ring-opening polymerization, via lanthanide catalysis, 4, 145... 

A final point regards the effect of lithium salts. Methyltitanium triisopropoxide 6, prepared from methyllithium and 3, reacts in situ with carbonyl compounds lightly slower than the distilled compound. However, this has no effect on chemoselectivity6. The only exception noted so far concerns allyl derivatives, as discussed in the following Section C.VII. 

The unique phenomena observed for allyltitanium ate complexes appear to be restricted to allyl groups. Reversal of chemoselectivity in methylation reactions has not been observed to date. Ate complexes of the type 122 and 123 react much faster with aldehydes than with ketones 90>, but the reactions are not as clean as with the allyl derivatives. Aromatic nitro and cyano groups are tolerated. In certain situations reversal of diastereoselectivity is possible using 123 (Sect. D.II). Ate complexes prepared from poly-titanates17) are also aldehyde selective.77 ... 

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