Synthesis Claisen rearrangement

Haddad, M. Molines, H. Wakselman, C. Preparation of P-Trifluoromethyl-Y-butyrolac-tones via Claisen Rearrangement. Synthesis 1994, 167-169. 

Majumdar KC, Bhattacharyya T, Chattopadhyay B, Sinha B. Recent advances in the aza-Claisen rearrangement. Synthesis 2009 (13) 2117-2142. 

Paquette, L.A. and Sweeney, T.J. (1990a) Stereospecific approach to 3-oxocen-7-ones via aliphatic Claisen rearrangement. Synthesis of (+)-(2R,8S)- and (+)-(2R,8/)-lauthisan. Tetrahedron. 46, 4487-4502. 

Kurth, M.J. and Soares, C.J. (1987) Asymmetric aza-Claisen rearrangement synthesis of (- -)-dihydropallescensin-2 [( )-penlan-pallescensin]. Tetrahedron Lett., 2, 1031-1034. 

The most recent, and probably most elegant, process for the asymmetric synthesis of (+)-estrone appHes a tandem Claisen rearrangement and intramolecular ene-reaction (Eig. 23). StereochemicaHy pure (185) is synthesized from (2R)-l,2-0-isopropyhdene-3-butanone in an overall yield of 86% in four chemical steps. Heating a toluene solution of (185), enol ether (187), and 2,6-dimethylphenol to 180°C in a sealed tube for 60 h produces (190) in 76% yield after purification. Ozonolysis of (190) followed by base-catalyzed epimerization of the C8a-hydrogen to a C8P-hydrogen (again similar to conversion of (175) to (176)) produces (184) in 46% yield from (190). Aldehyde (184) was converted to 9,11-dehydroestrone methyl ether (177) as discussed above. The overall yield of 9,11-dehydroestrone methyl ether (177) was 17% in five steps from 6-methoxy-l-tetralone (186) and (185) (201). 

H-Azepine, 2-allyloxytetrahydro-Claisen rearrangement, 7, 508 3H-Azepine, 2-amino-acylation, 7, 511 effect of acidification, 7, 510 nucleophilic displacement reactions, 7, 514 synthesis, 7, 533, 535 3H-Azepine, 2-amino-7-bromo-synthesis, 7, 529 3H-Azepine, 2-anilino-ring inversion, 7, 495-499 structure, 7, 533... 

Benzimidazole, 2-(2-phenylethyl)-synthesis, 5, 469 Benzimidazole, polychloro-synthesis, 5, 459 Benzimidazole, 2-propargylthio-Claisen rearrangement, 5, 446 Benzimidazole, 2-pyridyl-synthesis, 5, 471 Benzimidazole, 2-sodio-reactions, 5, 448 Benzimidazole, 2-(4-thiazolyl)-anthelmintic, 1, 181, 202 5, 498 biocide, 1, 399 fungicide, 1, 192... 

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. 

Thermal [3,3] Claisen rearrangement of the 3-substituted phenyl allyl and pro-pargyl ethers synthesis of 4-halobenzo[d]furans 98H(48)2173. 

The stereochemical outcome of the reaction is determined by the geometry of the transition state for the Claisen rearrangement a chairlike conformation is preferred,and it proceeds strictly by an intramolecular pathway. It is therefore possible to predict the stereochemical course of the reaction, and thus the configuration of the stereogenic centers to be generated. This potential can be used for the planning of stereoselective syntheses e.g the synthesis of natural products. 

Unlike the acid-catalyzed ether cleavage reaction discussed in the previous section, which is general to all ethers, the Claisen rearrangement is specific to allyl aryl ethers, Ar—O—CH2CH = CH2. Treatment of a phenoxide ion with 3-bromopropene (allyl bromide) results in a Williamson ether synthesis and formation of an allyl aryl ether. Heating the allyl aryl ether to 200 to 250 °C then effects Claisen rearrangement, leading to an o-allylphenol. The net result is alkylation of the phenol in an ortho position. 

Two other important sigmatropic reactions are the Claisen rearrangement of an allyl aryl ether discussed in Section 18.4 and the Cope rearrangement of a 1,5-hexadiene. These two, along with the Diels-Alder reaction, are the most useful pericyclic reactions for organic synthesis many thousands of examples of all three are known. Note that the Claisen rearrangement occurs with both allylic aryl ethers and allylic vinylic ethers. 

A salient structural feature of intermediate 18 (Scheme 2b), the retrosynthetic precursor of aldehyde 13, is its y,r5-unsaturated ester moiety. As it turns out, the Johnson ortho ester variant of the Clai-sen rearrangement is an excellent method for the synthesis of y,<5-unsaturated esters.11 In fact, the Claisen rearrangement, its many variants included, is particularly valuable in organic synthesis as a method for the stereocontrolled construction of trans di- and tri-substituted carbon-carbon double bonds.12,13 Thus, it is conceivable that intermediate 18 could be fashioned in one step from allylic alcohol 20 through a Johnson ortho ester Claisen rearrangement. In... 

N,O-acetal intermediate 172, y,<5-unsaturated amide 171. It is important to note that there is a correspondence between the stereochemistry at C-41 of the allylic alcohol substrate 173 and at C-37 of the amide product 171. Provided that the configuration of the hydroxyl-bearing carbon in 173 can be established as shown, then the subsequent suprafacial [3,3] sigmatropic rearrangement would ensure the stereospecific introduction of the C-37 side chain during the course of the Eschenmoser-Claisen rearrangement, stereochemistry is transferred from C-41 to C-37. Ketone 174, a potential intermediate for a synthesis of 173, could conceivably be fashioned in short order from epoxide 175. 

Isomerization of vinylaziridines is widely used in organic synthesis. Six types of isomerization of vinylaziridines are shown in Scheme 2.40. Outlined in this section are i) azepine formation by aza-[3,3]-Claisen rearrangement of 1,2-divinyl- or 2,3-divinylaziridines 153 (Section 2.4.1), ii) pyrroline formation from 155 (Section 2.4.2), Hi) aza-[2,3]-Wittig rearrangement of anionic species 157 (Section 2.4.3),... 

Thio-Claisen rearrangement 746-748 Thioketene 5-oxides photolysis of 878 reactions of 277 Thiolane dioxides formula of 382 NMR spectra of 460 reactions of 604 synthesis of 461 Thiolane oxides 747 formula of 382 IR spectra of 461 synthesis of 461, 462, 752 Thiolanes, photolysis of 881 Thiolene dioxides formula of 382 NMR spectra of 460 reactions of 464, 465 synthesis of 461 Thiolene oxides formula of 382 synthesis of 461, 746 Thiols... 

Because of the nature of the transition state in the pericyclic mechanism, optically active substrates with a chiral carbon at C-3 or C-4 transfer the chirality to the product, making this an enantioselective synthesis (see p. 1451 for an example in the mechanistically similar Claisen rearrangement). ... 

Nubbemeyer U (2001) Synthesis of Medium-Sized Ring Lactams. 216 125-196 Nubbemeyer U (2005) Recent Advances in Charge-Accelerated Aza-Claisen Rearrangements. 244 149-213... 

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