Allyl chloride Claisen rearrangement

Compound 1, 2,2-diniethyl-4-pentenal, has been prepared by the Claisen rearrangement route described above and by reaction of isobutyraldehyde with allyl chloride in the presence of aqueous sodium hydroxide and a phase-transfer catalyst. Both routes are applicable to the synthesis of a variety of substituted 4-pentenals. 

Ether groups in the benzene ring of quinazoline behave as in ethers of homocyclic aromatic compounds, e.g., they can be demethylated with anhydrous aluminum chloride. Allyl ethers also undergo a Claisen rearrangement/ ... 

Rearrangement of allyl trimethylsilyl ketene acetal, prepared by reaction of allylic ester enolates with trimethylsilyl chloride, to yield Y,5-unsaturated carboxylic a-cids. The Ireland-Claisen rearrangement seems to be advantageous to the other variants of the Claisen rearrangement in terms of E/Z geometry control and mild conditions. 

Usually, one would expect that an acrylate ester would be prepared by the acylation of an alcohol with acryloyl chloride. Jonathan M.J. Williams of the University of Bath reports (Tetrahedron Lett. 44 5523,2003) that this acylation can also be effected with the mild combination of Ph,P and maleic anhydride. The acrylate esters so prepared are interesting as polymerization precursors, and as Diels-Alder dienophiles. The allylic acrylates invite tandem conjugate addition / Ireland Claisen rearrangement. 

Allyl 2,2,2-lrifluoroethyl ethers 36 are obtained from the alkoxides and cinnamyl chloride (for 36a) or allyl bromide (for 36b).17 Claisen rearrangement of the vinyl ethers 37 is complete within one to several hours at 80 C to give a, -difluoro aldehyde 38a or ketone 38b. 

The chelated ester enolate Claisen rearrangement of allylic glycinates 9 is carried out with zinc(II) chloride, which is added to the enolate at — 78 C (Table 19). The rearrangement occurs as the reaction mixture is allowed to warm to room temperature over 1 hour. The 2-amino-3,3-difluoro-4-[(2-methoxyethoxy)methoxy] alk-4-enoic acids 10 arc converted directly into the corresponding methyl esters, which can be hydrolyzed to the methyl 2-amino-3,3-difluoro-4-oxoal-kanoates. 

Catalytic tandem isomerization/Claisen reaction of bis allyl ether was reported by Dixneuf et al. [23]. A cationic bis-oxazoline-ruthenium-arene complex S3 in the presence of both l,3-bis(2,6-diisopylphenyl)imidazolinium chloride and CS2CO3 catalyzes the selective transformation of bis-allyl ether 51 into ) c5-unsaturated aldehyde 52 via successive alkene isomerization and Claisen rearrangement (Eq. 12.21). 

The efficient addition of allylic bromides to carbonyl compounds in a heated zinc column has been used to synthesize ( )-artemisia alcohol (81 R = H, X = CH2) in 91% yield.Artemisia ketone was synthesized efficiently from 3-methyl-l-trimethylsilylbut-2-ene and 3-methylbut-2-enoyl chloride in the presence of AlCls. Racemic methyl santolinate (82) was synthesized (along with the C-3 epimer ratio 8 1) via Claisen rearrangement, according to Scheme 2 (cf. Vol. 6, p. 7). ... 

These two milestone syntheses were soon followed by others, and activity in this field continued to be driven by interest in the biologically active esters of cephalotaxine. In 1986, Hanaoka et al. (27) reported the stereoselective synthesis of ( )-cephalotaxine and its analog, as shown in Scheme 4. The amide acid 52, prepared by condensation of ethyl prolinate with 3,4-dimethoxyphenylacetyl chloride, followed by hydrolysis of the ethyl ester, was cyclized to the pyrrolobenzazepine 53 by treatment with polyphos-phoric acid, followed by selective O-alkylation with 2,3-dichloropropene (54) in the presence of sodium hydride. The resulting enol ether 55 underwent Claisen rearrangement on heating to provide C-allylated compound 56, whose reduction with sodium borohydride yielded the alcohol, which on treatment with 90% sulfuric acid underwent cationic cyclization to give the tetracyclic ketone 57. Presumably, this sequence represents the intramolecular version of the Wichterle reaction. On treatment with boron tribromide, ketone 57 afforded the free catechol, which was reacted with dibromometh-ane and potassium fluoride to give methylenedioxy derivative 58, suited for the final transformations to cephalotaxine. Oxidation of ketone 58... 

Knight s synthesis of ( ) -a-kainic acid provides aheterocyclic example.38 The starting material for the Claisen rearrangement is made from natural aspartic acid coupled to an allylic chloride 198 with a protected allylic alcohol 200 also present. Deprotection and lactonisation gives the nine-membered nitrogen-containing lactone 201. 

But-2-enyl)phenol readily formed an allyl ether in quantitative yield when its sodium salt was reacted with allyl chloride. This compound underwent Claisen rearrangement at 200°C to afford 2-allyl-4-but-2-enylphenol, the allyl ether of which, in turn, was rearranged to give 2,6-diallyl-4-but-2-enylphenol. Selective isomerisation of the allyl groups of this compound took place by heating at 110°C to afford 2,6-dipropenyl-4-but-2-enylphenol (ref.102). 

Stille and co-worker developed an attractive route to aza-Claisen precursors. Allylamine reacted with 2-methylpropanal (isobutyraldehyde), for example, to give allylimine 658. When this reacted with 2-methylpropanoyl chloride, N-acyl derivative 659 was produced (94% overall yield from allylamine) and reduction with LiAlH4 give a 98% yield of the tertiary amine, 660. Stille found that conversion of the amine to the ammonium salt by treatment with HCl led to clean conversion to 661 in 82% yield via a [3,3]-sigmatropic rearrangement (an aza-Claisen rearrangement). Reduction of the iminium salt led to an 81% yield of 662 from 661. Stille and co-workers also found that Lewis acids as well as HCl react with the allyl enamine precursor to facilitate the aza-Claisen rearrangement. 2... 

Treatment of allyl sulfide 111 with dichloroketene, generated in situ by reductive elimination of chlorine from trichloroacetyl chloride, results in an intramolecular ketene Claisen rearrangement giving 779 with high, 2-syn selectivity (94% de). Reductive dechlorination and subsequent lactonization affords chiral butyrolactone 780, with an optical purity that exceeds 95%. 

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