Showing papers on "Claisen rearrangement published in 1975"
30 citations
TL;DR: The natural coumarins, sesibiricin and toddaculin, were synthesised from 5,7-dihydroxy-7methoxycoumarin this article.
24 citations
TL;DR: The synthesis of the title compounds from butynylcarbinols 5 with 1-dimethylamino-1-methoxy-1propene in a Claisen rearrangement via the amides 7 is described in this article.
Abstract: Die Synthese der Titelverbindungen aus den Butinylcarbinolen 5 mit 1-Dimethylamino-1-methoxy-1-propen in einer Claisen-Umlagerung uber die Amide 7 wird beschrieben. Eine effektive Darstellung der Ausgangsverbindungen wird angegeben, und die Daten der Produkte werden mit den aus Naturstoffen gewonnenen verglichen.
The Synthesis of 5α-Stigmasta-22,25-dien-3β-ol, 5α-Stigmast-22-en-3β-ol und 5α-Stigmastan-3β-ol and their 24-Epimers
The synthesis of the title compounds from butynylcarbinols 5 with 1-dimethylamino-1-methoxy-1-propene in a Claisen rearrangement via the amides 7 is described. An effective preparation of the starting materials is given and the data of the products are compared with those from natural sterols.
13 citations
TL;DR: In coexistence with TiCl4 and N-trimethylsilylacetanilide, allyl aryl ethers involving 2-butenyl phenyl ethers and 3-methyl-2-butensyl 2-phenyl ether were rearranged under mild conditions to afford allyl phenols in good yields.
Abstract: In coexistence with TiCl4 and N-trimethylsilylacetanilide, allyl aryl ethers involving 2-butenyl phenyl ether and 3-methyl-2-butenyl phenyl ether were rearranged under mild conditions to afford allyl phenols in good yields.
12 citations
TL;DR: In this paper, three new bridged ketones, 7,8 and 9, have been isolated by heating 2,2′-bis-allyloxy-1,1′-binaphthyl (5) at 215° for 16 hours.
Abstract: Intramolecular cyloadditions of binaphtyl compounds
Three new bridged ketones, 7,8 and 9, have been isolated in 44%, 3% and 19% yields respectively (Scheme 2) by heating 2,2′-bis-allyloxy-1,1′-binaphthyl (5) at 215° for 16 hours. These compounds could be epimerized about C(16) by bases, and in particular 9 yielded the new epimer 10. The structures of the alcohols obtained by reduction of the keto group are also given (Scheme 2). The constitution of all compounds was derived from spectroscopic data, chiefly from their 1H-NMR, spectra (tab. 2, 3 and fig. 1). The assignments were based on the observed long-range coupling constant between H(endo)-C(16) and H(endo)-C(5) in 7 and 10 and on the analysis of chemical shifts and coupling constants in both the ketones and their derivatives. Moreover, the structures of the compounds investigated have been proved by x-ray analysis of ketone 8 (chap. 3, fig. 2). The thermal conversion of binaphthylether 5 to the bridged ketones proceeds via an intramolecular Diels-Alder reaction, followed by Claisen rearrangement (Scheme 8). On heating, the bis-beta-methylallyl ether 20 yielded the ketone 21 and a small amount of the ether 23 (Schemes 5 and 7). Ether 23 and binaphthyl monoallyl ether 26 were converted thermally to the bridged ketones 31 (Scheme 7) and 27 (Scheme 6) respectively. In addition, 26 underwent an intramolecular ene-reaction to give the spiroketone 28 (Schemes 6 and 9). The structures of these compounds were also established, mainly by analysis of their 1H-NMR. spectra.
12 citations
TL;DR: The half-life times for thermal rearrangement of a series of carcinogenic N, O -diacetyl- N -arylhydroxylamines have been studied and the rate of rearrangements correlates with the extent of aryl conjugation and the degree of electron density in the N - Daryl-moiety.
11 citations
9 citations
TL;DR: The Claisen rearrangement of 7-O-cinnamyl noreugenin (2) yields 4′,5′ - dihydro - 5 - hydroxy - 2,4′ - dimethyl - 5′ - phenyl - furo (2′,3′: 7,8) chromone as established by its NMR spectrum as discussed by the authors.
7 citations
5 citations
TL;DR: The total synthesis of celebixanthone methyl ether [1,5-dihydroxy-6,7-dimethoxy-8-(3-methylbut-2-enyl)xanthen-9-one] is described in this article.
Abstract: The total synthesis of celebixanthone methyl ether [1,5-dihydroxy-6,7-dimethoxy-8-(3-methylbut-2-enyl)xanthen-9-one](2) is described. The route involves preparation of 2-hydroxy-2′,3,4,5,6′-pentamethoxybenzophenone (8) and subsequent base catalysed cyclisation to give 1,5,6,7-tetramethoxyxanthen-9-one (4). Selective demethylation and methylation gives 1,5-dihydroxy-6,7-dimethoxyxanthen-9-one (3). Preparation of the 5-(3-methyl-2-butenyloxy)xanthen-9-one (10) followed by a Claisen rearrangement gives celebixanthone methyl ether.
3 citations
TL;DR: The kinetics of the Claisen rearrangement of trans-cinnamyl aryl ethers with substituents OR both benzene rings has been investigated in this article.
TL;DR: Chung et al. as discussed by the authors showed that p-hydroxybenzaldehyde and 3-chloro-3-methyl-2-butenyl-1-butyne (III) gave 4-(1,1-dimethylpropargyloxy)benzldehyde (VIII), which was catalytically hydrogenated over Lindlar catalyst to afford 4-( 1,1]-dimethylallyloxy (IX) benzaldehyde (X) by Claisen rearrangement.
Abstract: Sophoradin (I) [2′,4,4′-trihydroxy-3,3′,5-tris(3-methyl-2-butenyl)chalcone] which had been isolated from “Guang-Dou-Gen” (the root of Sophora subprostrata Chun et T Chen) was synthesized through Claisen rearrangement The reaction of p-hydroxybenzaldehyde and 3-chloro-3-methyl-1-butyne (III) gave 4-(1,1-dimethylpropargyloxy)benzaldehyde (VIII), which was catalytically hydrogenated over Lindlar catalyst to afford 4-(1,1-dimethylallyloxy)benzaldehyde (IX) IX was converted to 4-hydroxy-3-(3-methyl-2-butenyl)benzaldehyde (X) by Claisen rearrangement The reaction of X and III gave 3-(3-methyl-2-butenyl)-4-(1,1-dimethylpropargyloxy)benzaldehyde (XI) Condensation of 2-hydroxy-4-(1,1-dimethylpropargyloxy)acetophenone (IV) and XI in alkaline solution gave a chalcone (XIII), which was catalytically hydrogenated over Lindlar catalyst to give 2′-hydroxy-4,4′-bis(1,-dimethylallyloxy)-3-(3-methyl-2-butenyl)chalcone (XIV) XIV was converted to I by Claisen rearrangement
TL;DR: In this article, the pyrimidine system can be functionalized at C-5 by thio-Claisen rearrangement of 3-substituted 4-allylthiopyrimidin-2-ones.
Abstract: Functionalization at C-5 of the pyrimidine system can be achieved by thio-Claisen rearrangement of 3-substituted 4-allylthiopyrimidin-2-ones.
TL;DR: Transetherification of sclareol (labd-14-ene-8,13-diol) with triethyl orthoacetate and subsequent rearrangement gave (E)- and (Z)-ethyl 8-hydroxylabd-13-en-15-ylacetate (2) and (R = CO2Et).
Abstract: Transetherification of sclareol (labd-14-ene-8,13-diol)(1) with triethyl orthoacetate and subsequent rearrangement gave (E)- and (Z)-ethyl 8-hydroxylabd-13-en-15-ylacetate (2) and (3)(R = CO2Et). Products of cyclisation of these esters with tin(IV) chloride in benzene were characterised. Similar reactions with sclareol monoacetate (11) are described and stereochemical implications are discussed.
TL;DR: Allyl 2-naphthyl sulphoxide undergoes thermal rearrangement to give a dihydronaphthothiophen derivative as mentioned in this paper, which can be used to give dihydrophythyl sulfoxide.
Abstract: Allyl 2-naphthyl sulphoxide undergoes thermal rearrangement to give a dihydronaphthothiophen derivative.