Allyl phenyl ethers, Claisen rearrangement

Claisen rearrangement org chem A thermally induced sigmatrophic shift In which an allyl phenyl ether is rearranged to yield an orffio-allylphenol. kla son, re-o ranj-mont ... 

Q The mechanism of the Claisen rearrangement of other allylic ethers of phenol is analogous to that of allyl phenyl ether What is the product of the Claisen rearrangement of C6H50CH2CH CHCH3 /... 

Claisen rearrangement (Section 24 13) Thermal conversion of an allyl phenyl ether to an o allyl phenol The rearrange ment proceeds via a cyclohexadienone intermediate... 

CLAISEN - IRELAND Rearrangment Rearrangement ol allyl phenyl ethers to o (or p-)allylphenols or of allyl vinyl ethers to y.S-unsaturated aldehydes or ketones (Claisen) Rearrangement ol allyl esters as enolale anions to y.S-unsaturated acids (Ireland)... 

Problem 30.9 When a 2,6-disubslituted allyl phenyl ether is heated in an attempted Claisen rearrangement, migration occurs to give the />-allyl product as the result of two sequential pericyclic reactions. Explain. 

The basic pattern of the Claisen rearrangement is the conversion of a vinyl allyl ether to a y,8-enone. The reaction is also observed for allyl phenyl ethers, in which case the products are o-allylphenols. 

Wipf and coworkers used a Claisen rearrangement of allyl phenyl ethers 4-309 followed by an enantioselective carboalumination using the chiral Zr-complex 4-310 and trimethyl aluminum (Scheme 4.67) [104]. After an oxidative work-up of the intermediate trialkylalane, the corresponding alcohols 4-311 were obtained with up to 80% ee and 78% yield. One can also transfer an ethyl group using triethyl aluminum with even better ee-values (up to 92%), but the yields were rather low (42%) due to a more sluggish oxidative cleavage of the Al-C bond. 

Allyl phenyl ether was heated with water in the MBR for 1 h at different temperatures [46]. It underwent Claisen rearrangement to 2-allylphenol (56% yield) at 200 °C, 2-(2-hydroxyprop-l-yl)phenol (37% yield) at 230 °C and 2-methyl-2,3-dihydro-furan (72% yield) at 250 °C (Scheme 2.12). Support for the reaction sequence was obtained through experiments with authentic intermediates. 

Claisen rearrangement of allyl phenyl ethers. These were thoroughly studied before the rearrangement of allyl vinyl ethers... 

Some allyl phenyl ethers with an alkyl substituent on the end carbon of the allyl group rearrange to give the normal ortho-Claisen product together with another isomeric O-allyl phenol. The latter, formed by the rearrangement of the normal product, has been established. This is called abnormal Claisen rearrangement, is illustrated by the following example. 

A unified theoretical explanation using molecular orbital theory has been proposed. Grimme [65] investigated the PFR of phenyl acetate as well as the photo-Claisen rearrangement of allyl phenyl ether and the 3-cleavage of para-substituted phenoxyacetones. A unified description of the three reactions has been invoked according to MNDOC-CI and AMl/AMl-HE calculations. No matter what ex-... 

Allyl phenyl ethers rearrange cleanly at high temperatures, producing 0-allyl phenols or -allylphenols if both ortho positions are blocked. This reaction is called the Claisen rearrangement (10). 

Substituted allyl aryl ethers undergo a Claisen rearrangement similar to the reaction described in text Section 24.13 for allyl phenyl ether. 2-Butenyl phenyl ether rearranges on heating to give o-( 1-methyl-2-propenyl)phenol. 

Ramamurthy and coworkers studied the photo-Fries rearrangement of phenyl acetate and phenyl benzoate and photo-Claisen rearrangement of allyl phenyl ether (Fig. 34) included in two types of zeolite (faujasites X and Y and pen-tasils ZSM-5 andZSM-11) [192], The photolysis was performed with the zeolite slurry in either hexane or iso-octane. One of the most remarkable observations is that the product distribution is altered within zeolites from that in isotropic solvent. Furthermore, while in solution, nearly a 1 1 mixture of ortho and para isomers 40 and 41 (Fig. 34) was obtained, within zeolites one is able to direct the photoreaction selectively toward either the ortho or the para products by conducting the reaction either within faujasites or pentasils, respectively (Fig. 34). 

Figure 34 Photo-Fries rearrangement of phenyl acetate and phenyl benzoate, and photo-Claisen reaction of allyl phenyl ether in solution and within zeolites.

Rapid Claisen rearrangement of allyl phenyl ether and meta-substituted derivatives has been reported to occur with poor regioselectivity at 250 °C in dicationic ionic liquids, especially (24).23 Claisen rearrangement of resorcinol allyl ethers (25) was found to have poor regioselectivity under thermal or microwave conditions, but it was further found that selectivity for the 6-substituted product (26) over (27) could be improved to 13 1 using boron trichloride and an appropriately protected ether (25 ... 

Verification of different theoretical methods used in calculations of transition states was thoroughly discussed by Singleton et al.60 on the basis of their own and published by others studies of Claisen rearrangement. The rearrangements of allyl vinyl ether (Equation (31)) and allyl phenyl ether (Equation (32)) were chosen for by the combined 2H, 13C and l70 isotope effects and calculation studies. 

The experimental KIEs were determined for the aliphatic Claisen rearrangement in p-cymene at 120°C and for the aromatic Claisen rearrangement either neat at 170°C or in diphenyl ether at 220°C. Changes in 2H, 13C or 170 composition were determined for unreacted substrates. For carbon analysis of allyl vinyl ether the C5 carbon was used as an internal standard. The C4 atom and rneta aryl protons were used as references in analysis of allyl phenyl ether. The 170 analysis was based on a new methodology. The results are summarized in Table 1, along with predicted isotope effects calculated for experimental temperatures by means of different computational methods. The absolute values of predicted isotope effects for C4 and C5 atoms varied with theoretical level and all isotope effects were rescaled to get reference effects equal to 1.000. 

Claisen rearrangement (Sections 18.4 and 30.8) the thermal [3.3] sigmatropic rearrangement of an allyl vinyl ether or an allyl phenyl ether. 

Rearrangement of 1,5-dienes is known as the Cope rearrangement and rearrangement of allyl phenyl ethers and allyl vinyl ethers is known as the Claisen rearrangement The... 

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