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Showing papers on "Claisen rearrangement published in 1991"



Journal ArticleDOI
TL;DR: La diastereoselectivite de la transposition est en accord avec un etat de transition de type chaise as discussed by the authors, a.k.a. transition of type chalice.
Abstract: La diastereoselectivite de la transposition est en accord avec un etat de transition de type chaise

121 citations


Book ChapterDOI
01 Jan 1991
TL;DR: In this paper, a survey of variants of the Claisen rearrangement that are of general use in stereoselective organic synthesis is presented, highlighting the influence of steric and electronic parameters on transition state geometries.
Abstract: This article surveys variants of the Claisen rearrangement that are of general use in stereoselective organic synthesis. Recent results concerning the influence of steric and electronic parameters on transition state geometries are highlighted. The impact of the Claisen methodology in modern synthetic strategy and its application for the preparation of highly functionalized derivatives is exemplified.

100 citations


Journal ArticleDOI
TL;DR: In this paper, the preference for chair-and boat-like transition state geometries in the ester enolate Claisen rearrangement of straight chain, carbocyclic, and heter-cyclic propanoates was investigated.
Abstract: The preference for chair- and boatlike transition-state geometries in the ester enolate Claisen rearrangement of straight chain, carbocyclic, and heterocyclic propanoates was investigated. A novel stereoelectronic effect in pyranoid and furanoid glycal systems leads to a significant relative stabilization of the boatlike vs the chairlike TS : . The preferred transition state in six- and five-membered carbocyclic systems is highly dependent on steric factors, as the energy difference between chair- and boatlike TS : tends to be small. With straight-chain substrates, a significant contribution of the boatlike TS : to the rearrangement product mixture is only expected in bis-donor substituted allylic esters

97 citations


Journal ArticleDOI
TL;DR: This is the first to show that meta-Claisen rearrangement occurs preferentially even when a free para position is available, and can be interpreted in terms of the small bond energy of the breaking apical carbon-iodine (III) bond.
Abstract: Reported for the first time are the generation of allenyliodinanes and their reductive iodonio-Claisen rearrangement Reaction of propargylsilanes, germanes, and stannanes with aryliodinanes in the presence of BF 3 -Et 2 O undergoes a reductive iodonio-Claisen rearrangement under mild conditions, yielding o-propargyliodoarenes in good yields The reductive ortho propargylation probably involves the intermediate formation of allenyl(aryl) iodinanes, which undergo [3,3]-sigmatropic rearrangement The lack of crossover products argues for the intramolecularity of the rearrangement When both ortho positions of aryliodinanes are occupied with alkyl substituents, the reductive iodonio-Claisen rearrangement affords meta substitution products This is the first to show that meta-Claisen rearrangement occurs preferentially even when a free para position is available The reductive ortho propargylation of iodinanes takes place under much milder conditions than the Claisen rearrangement The lower activation energy associated with the iodonio-Claisen rearrangement of allenyl(aryl) iodinanes can be interpreted in terms of the small bond energy of the breaking apical carbon-iodine (III) bond

65 citations


Journal ArticleDOI
TL;DR: Two new molecules were synthesized from the common intermediate 7 by a sequential coupling with N-benzoylalanine followed by a Claisen rearrangement.
Abstract: β-D-C-Allosyl-(R)-alanine 12 and β-D-C-altrosyl-(R)-alanine lactone 15 were synthesized from the common intermediate 7 in just a few steps. The β-C-glycosyloxazolone 7 was obtained in two steps from the protected D-glucal 4 by a sequential coupling with N-benzoylalanine followed by a Claisen rearrangement

58 citations


Journal ArticleDOI
TL;DR: In this article, the triisobutylaluminum-catalyzed Claisen rearrangement of a series of bicyclic allyl vinyl ethers was examined in connection with a planned synthesis of the diterpene epoxydictymene.
Abstract: The triisobutylaluminum-catalyzed Claisen rearrangement of a series of bicyclic allyl vinyl ethers was examined in connection with a planned synthesis of the diterpene epoxydictymene. The exocyclic vinyl ethers studied undergo [3,3] sigmatropy via chairlike transition states to provide products having Z stereochemistry about the double bond of the eight-membered ring. Differences appear only in the extent of stereoselectivity in the ensuing carbonyl reduction step. Two companion endocyclic vinyl ethers were found to utilize boat transition states to deliver Z products exclusively. In all cases, the level of chirality transfer is excellent

49 citations


Journal ArticleDOI
TL;DR: The reaction of α-azido acetate (R-1i) is the first example of a Claisen rearrangement involving an α-AZido ester and results in a new approach toward the asymmetric synthesis ofα-amino acids.
Abstract: The Ireland ester Claisen rearrangement of chiral (R)- and (S)-C3-(acyloxy)-(E)-vinylsilanes gives access to a wide range of α-chiral-β-silyl-(E)-hexenoic acids with useful levels of diastereoselectivity for both the 2,3-syn and 2,3-anti diastereomers as illustrated in eqs 1 and 2. The vicinal diastereoselectivities for simple propionate esters rac-1b, (S)-1e, and (R)-1g can be varied from 1:12 to 16:1 (syn:anti) depending on reaction conditions. The employment of appropriately protected glycolate esters yields Claisen products with diastereoselectivities ranging from 23:1 (syn:anti), resulting from chelation control of enolate geometry, to 1:3.6 (syn:anti) via the use of a nonchelating, silicon-protecting group. The reaction of α-azido acetate (R)-1i is the first example of a Claisen rearrangement involving an α-azido ester and results in a new approach toward the asymmetric synthesis of α-amino acids

44 citations



Journal ArticleDOI
TL;DR: In this paper, the authors compose du titre a partir d'5-isopropyl-2-methylcyclopent-1-ene carbaldehyde via the transposition Claisen d'un derive de cyclopenta pyrane en derive decyclopenta cyclooctene.
Abstract: Synthese du compose du titre a partir d'5-isopropyl-2-methylcyclopent-1-ene carbaldehyde via la transposition Claisen d'un derive de cyclopenta pyrane en derive de cyclopenta cyclooctene

42 citations


Journal ArticleDOI
TL;DR: In this article, the total synthesis of the denticulatins was described and the key feature was the efficient generation of the C-1-to-C-9 building block by three consecutive stereoselective carbon - carbon bond-forming steps using chiral allylboronates.
Abstract: The total synthesis of the denticulatins 1 is described. Key feature is the efficient generation of the C-1-to-C-9 building block 37 by three consecutive stereoselective carbon - carbon bond-forming steps using chiral allylboronates. The C-10-to-C-17 building block was obtained by kinetic Sharpless resolution of an allylic alcohol followed by an Ireland-Claisen rearrangement.

Journal ArticleDOI
TL;DR: In this paper, it was shown that the chiral auxiliary directed the approach of the crotyl fragment to the Si face of the (E )-N,O -ketene acetal.

Journal ArticleDOI
TL;DR: An advanced intermediate for the synthesis of the Laurencia oxonane natural product obtusenyne, namely the unsaturated nine-membered lactone 3, was efficiently prepared in seven steps from (E )-3-hexenoic acid as mentioned in this paper.


Journal ArticleDOI
TL;DR: Iminophosphoranes 4, derived from ethyl alpha-azido-2-(allyloxy)-3-methoxycinnamates react with ketenes to give the corresponding ketene imines to give isoquinoline derivatives 7 and/or the previously unknown fluoreno[2,3,4-ij]isoquinolines 9 in moderate yields.
Abstract: Iminophosphoranes 4, derived from ethyl alpha-azido-2-(allyloxy)-3-methoxycinnamates, react with ketenes to give the corresponding ketene imines, which by thermal treatment at 150-160-degrees-C undergo a consecutive electrocyclic ring closure/Claisen rearrangement/second ring closure/double aromatization process to give isoquinoline derivatives 7 and/or the previously unknown fluoreno[2,3,4-ij]isoquinolines 9 in moderate yields. Similarly, iminophosphoranes 14 derived from ethyl alpha-azido-2,3-disubstituted-4-(allyloxy)cinnamates reacted with diphenyl ketene to give the intermediate ketene imines, which at 150-160-degrees-C undergo a cascade of pericyclic reactions to give the isoquinolines 15 and the pentacyclic compounds 16 in moderate yields.

Journal ArticleDOI
TL;DR: The selective formation of the required α- fluoro silyl ketene acetal 3 was found to result from the stereoselective rearrangement of the allyl α-fluoro-α-silylacetate isomer, unexpected as stereoselectedive deprotonation of fluoroacetates is not normally possible.
Abstract: The ester enolate Claisen rearrangement of allyl α-fluoroacetates 1 forms 2-fluoroalkenoic acids 2 in good to excellent yield with good internal asymmetric induction. This selectivity was unexpected as stereoselective deprotonation of fluoroacetates is not normally possible. The selective formation of the required α-fluoro silyl ketene acetal 3 was found to result from the stereoselective rearrangement of the allyl α-fluoro-α-silylacetate isomer. Although silyl ketene acetals derived from α-fluoropropanoates 7 also rearranged, control of internal asymmetric induction was not possible

Journal ArticleDOI
TL;DR: The asymmetric Claisen rearrangement of allyl vinyl ethers has been effected with a chiral organoaluminum reagent, ( R )-1 or ( S )- 1 as an example of the enantioselective activation of ether substrates.
Abstract: The asymmetric Claisen rearrangement of allyl vinyl ethers has been effected with a chiral organoaluminum reagent, ( R )- 1 or ( S )- 1 as an example of the enantioselective activation of ether substrates. This method provides a facile asymmetric synthesis of various acylsilanes and acylgermanes with high optical purity. Among various trialkylsilyl substituents of chiral organoaluminum reagent 1 , use of the more bulky t -butyldiphenylsilyl group exhibits the highest enantioselectivity. The conformational analysis of two possible chairlike transition-state structures of an allyl vinyl ether substrate reveals that a chiral organoaluminum reagent 1 can discriminate between these two conformations only by a difference in the orientation of α-methylene groups of ethers.


Journal ArticleDOI
TL;DR: The metalla-Claisen rearrangement reported in this paper leads to 1,1-dimetallic compounds where three asymmetric centers are obtained with good diastereoselection.

Journal ArticleDOI
TL;DR: In this paper, the utility of phosphine oxide and phosphonate groups has been examined in the context of the carbanion-accelerated Claisen rearrangement (CACR), which permits the construction of substituted allyl vinyl ethers by allyl oxide addition to phosphorus-substituted allenes.
Abstract: The utility of phosphine oxide and phosphonate groups has been examined in the context of the carbanion-accelerated Claisen rearrangement (CACR). Both of the groups permit the construction of substituted allyl vinyl ethers by allyl oxide addition to phosphorus-substituted allenes. Extensive optimization was required to suppress isomerization of both the allenes and the vinyl ethers. Using potassium dimsylate and lithium chloride as the base, both the phosphine oxides and phosphonates rearranged readily at room temperature with complete regioselectivity in good yield (62-93%). The phosphonates also showed a high level of diastereoselectivity (92% de). The characteristic features of the CACR were compared with the original arylsulfone version

Journal ArticleDOI
TL;DR: In this article, a transition state model is proposed to explain the observed asymmetric induction by the external hydroxy group as a result of both steric and stereoelectronic control.

Journal ArticleDOI
TL;DR: In this paper, an extremely mild 3-aza-Claisen reaction has been developed to convert Nallyl amides to pentenylnitriles in moderate to good yields by a transformation that occurs at room temperature under essentially neutral conditions.

Journal ArticleDOI
TL;DR: In this article, allylic benzodioxinic alcohols were prepared from 1,4-benzodioxin and then submitted to the orhoester Claisen rearrangement and Eschenmoser procedure leading to 3-substituted-2-alkylidene-1,4 -benzioxans.


Journal ArticleDOI
TL;DR: A new chlorin dicarboxylic acid 3 has been synthesized from the porphyrin 1 by amide acetal Claisen rearrangement as mentioned in this paper, which is a promising camdidate for application in Photodynamic Tumor Therapy (PDT).

Journal ArticleDOI
TL;DR: The orthoester Claisen rearrangement is used as a key reaction in the facile conversion of an acetaldehyde moiety stereospecifically into the (E)-4-methylhex-4-enoic acid side-chain of mycophenolic acid as discussed by the authors.
Abstract: The orthoester Claisen rearrangement is used as a key reaction in the facile conversion of an acetaldehyde moiety stereospecifically into the (E)-4-methylhex-4-enoic acid side-chain of mycophenolic acid.

Journal ArticleDOI
TL;DR: In this article, the authors describe the use of Wittig rearrangements to the construction of 2-desoxy-2-methylenebicyclomycin (3) and bicyclo.
Abstract: Bridgehead carbanion generation of bicyclo[5.2.2] and bicyclo[7.2.2] allyl ether bridged piperazinediones result in novel ring contractions via unusual [2,3] Wittig type and [3,3] Claisen rearrangements. The application of the [2,3] Wittig rearrangements to the construction of 2-desoxy-2-methylenebicyclomycin (3) is described. Introduction Bicyclomycin (1) is a commercially significant antimicrobial natural product' that has been the subject of numerous synthetic: mechanistic,j and biological4 studies. Maag and associatesS (1) For a review, see: Williams, R. M.: Durham, C. A. Chem. Reo. 1988, 88, 511 . (2) (a) Dunkerton, K. V.; Ahmed, R. M. Tetrahedron Lett. 1980,21, 1803. (b) Nakatsuka, S.: Yoshida, K.; Goto, T. Tetrahedron Left. 1981,22, 2009. (c) Williams, R. M. Tetrahedron Left. 1981, 22, 2341. (d) Shin, C.: Sato, Y.: Yoshimura, J. Tetruhedron Lett. 1981, 22, 2401. (e) Nakatsuka, S.: Yoshida, K.: Goto, T. Tetrahedron Lett. 1981, 22,4973. (f) Fukuyama, T.; Robins, B. D.; Sachleben, R. A. Tefrahedron Lett. 1981,22,4155. (g) Hoare, J . H.: Yates, P. J . Chem. SOC., Chem. Commun. 1981, 126. (h) Yates, P.: Hoare, J . H. Can. J . Chem. 1983, 61, 519. (i) [bid. 1983, 61, 1397. 6 ) Dirlam, J. P.: James, R. B.; Shoop, E. V., 185th National Meeting of the American Chemical Society, Seattle, WA, March 1983. Division of Organic Chemistry Abstr. 009. (k) Williams, R. M.: Anderson, 0. P.; Armstrong, R. W.: Josey, J.: Meyers, H.: Ericksson, C. J. Am. Chem. Soc. 1982,104,6092. ( I ) Williams, R. M.; Dung, J-S.; Josey, J.: Armstrong, R. W.: Meyers, H. J . Am. Chem. Soc. 1983,105,3214. (m) Sera, A.: Itoh, K.: Yamada, H.; Aoki, R. Heferocycles 1984, 22,713. (n) Sato, Y.: Shin, C.: Sumiya, S.: Nakajima, Y.; Yoshimura. J . Bull. Chem. SOC. Jpn. 1984, 57, 1265. ( 0 ) Shin, C.: Nakajima, Y.; Sato, Y. Heferocycles 1985, 23, 2217. (p) Walker, F. J. Ph.D. Thesis, Yale University, New Haven, CT, 1981. (9) Uang, B-J. Ph.D. Thesis, Yale University, New Haven, CT, 1986. (r) Dung, J-S.: Armstrong, R. W.: Williams, R. M. J . Org. Chem. 1984,49, 3416. (s) Maruyama-Kirms, L. K.: Williams, R. M. J . Org. Chem. 1987,52,4044. See also: Maruyama-Kirms, L. K. Ph.D. Thesis, Colorado State University, Fort Collins, CO, 1987. (t) Williams, R. M.: Kwast, A. J . Org. Chem. 1988,53, 5785. (u) Nakatsuka. S.: Yamada. K.; Yoshida, K.: Asano, 0.: Murakami, Y.: Goto, T. Tefrahedron Left. 1983,24, 5627. (v) Nakatsuka, S.: Goto, T. Heterocycles 1984, 21,61. (w) Nakatsuka, S. Pharmacia 1985, 21, 324. (x) Williams, R. M.; Armstrong, R. W.; Dung, J-S. J . Am. Chem. Soc. 1984, 106,5748. (y) Williams, R. M.; Armstrong, R. W.: Dung, J-S. J . Am. Chem. SOC. 1985, 107, 3253. (z) Williams, R. M.; Armstrong, R. W.: Maruyama, L. K.; Dung, J-S.; Anderson, 0. P. J . Am. Chem. SOC. 1985, 107, 3246. Wacker, 0.; Kump, W.: Muller, B. W. Tefrahedron Left. 1983,24,5607. (aa) Armstrong, R. W. Ph.D. Thesis, Colorado State University, Fort Collins, CO, 1984. (bb) Yamaura, M.: Suzuki, T.; Hashimoto, H.: Yoshimura, J.; Shin, C. Chem. Lett. 1984, 1547. (cc) Yoshimura, J.; Yamaura, M.: Suzuki, T.; Hashimoto, H. Chem. LPtl. 1984, 2157. (dd) Yamaura, M.; Suzuki, T.; Hashimoto, H.: Yoshimura, J.: Shin, C. Bull. Chem. Soc. Jpn. 1985,58, 2812. (ee) Yamaura, M.: Nakayama, T.; Hashimoto, H.: Shin, C.: Yoshimura, J.: Kodama, H. J. Org. Chem. 1988,53,6035. (ff) Dung, J-S.: Armstrong, R. W.; Anderson, 0. P.; Williams, R. M. J . Org. Chem. 1983, 48, 3592. (gg) Yoshimura, J.; Hara, K.; Yamura, M.: Mikami, K.: Hashimoto, H. Bull. Chem. SOC. Jpn. 1982.55,933. (hh) Dawson, 1. M.; Gregory, J. A.: Herbert, R. B.: Sammes, P. G. J . Chem. Soc.. Chem. Commun. 1986, 620.(3) (a) Someya, A.: Iseki, M.: Tanaka, N. J . Anfibiof. 1979,32,402. (b) Williams, R. M.; Tomizawa, K.: Armstrong, R. W.; Dung, J-S. J . Am. Chem. SOC. 1985, 107, 6419. (c) Williams, R. M.: Tomizawa, K.: Armstrong, R. W.: Dung, J-S. J. Am. Chem. Soe. 1987, 109,4028. (d) Kohn, H.; Abuzar, S. J. Am. Chem. SOC. 1988, 110, 3661. (e) Abuzar, S.: Kohn, H. J. Am. Chem. SOC. 1988, 110,4089. (0 Abuzar, S.; Kohn, H. J. Org. Chem. 1989, 54, 4000. (8) Kohn, H.; Abuzar, S. J . Org. Chem. 1988, 53, 2769. (h) Abuzar, S.: Kohn. H. J. Am. Chem. Soc. 1990, 112, 3114. (4) (a) Tanaka, N.: Iseki, M.: Miyoshi, T.: Aoki. H.: Imanaka, H. J. Antibiot. 1976, 29, 155. (b) Tokuma, Y.; Koda, S.: Miyoshi, T.: Morimoto, Y. Bull. Chem. SOC. Jpn. 1974,47, 18. (c) Miyoshi, T.: Iseki, M.: Konomi, T.: Imanaka, H. J. Anfiblot. 1980, 33, 480. (d) Iseki, M.: Miyoshi, T.: Konomi, T.; Imanaka, H. J . Antibiof. 1980. 33,488. (e) &hi, K.: Tsurumi, Y.: Shigematsu, N.: Iwami, M.; Umehara, K.; Okuhara, M. J . Antibiot. 1988, 41, 1106. (0 Someya, A.; Tanaka, K.: Tonaka, N. Antimicrob. Agents Chemother. 1979, 16,87. (g) Someya, A,: Iseki, M.: Tanaka, N. J . Antibiot. 1978, 31, 712. (h) Muller, B. W.: Zak, 0.: Kump, W.; Tosch, W.; Wacker, 0. J . Anfibiof. 1979, 32, 689. 0002-7863/91/1513-6621%02.50/0 demonstrated over 10 years ago that bicyclomycin undergoes a thermodynamically driven bis-spiro ring-forming dehydration to the tricyclic substances 2. The significance of the putative (leucyland isoleucyl-derived) amino acid oxidation states a t the a-positions (both carrying oxygenation) has been the subject of several provocative studies3v6 and remains an unresolved issue requiring further experimental clarification.


Journal ArticleDOI
TL;DR: The Stereoselective Ciaisen rearrangement of a series of tertiary allylic sulphone esters is reported in this article, where the rearrangements are based on the Stereodelective Caisen decomposition.
Abstract: The Stereoselective Ciaisen rearrangement of a series of tertiary allylic sulphone esters is reported.

Journal ArticleDOI
TL;DR: In this paper, the synthesis of the potent potassium channel opener Ro 31-6930 is described, and methods of controlling the regiochemistry of the crucial cyclisation are described.