A cycloaddition approach to tricyclic taxoid skeletons

Lu, Yee-Fung; Fallis, Alex G.

doi:10.1139/v95-278

Cited by 20 publications

(11 citation statements)

References 22 publications

(12 reference statements)

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“…13 C NMR spectra were recorded on the same instrument at 100MHz using the same solvent and internal reference. Chemical shift is reported in δ (PPM).…”

Section: Experimental Generalmentioning

confidence: 99%

Synthesis, characterization and spectral studies of various newer long chain aliphatic acid (2-hydroxy benzylidene and 1H-indol-3-ylmethylene) hydrazides as mosquito para-pheromones

Awasthi¹,

Rishishwar²,

Rao³

et al. 2007

Journal of the Korean Chemical Society

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ABSTRACT. Various long chain aliphatic acid hydrazides react with aromatic and heterocyclic aldehydes in alcoholic medium in refluxing conditions to give corresponding 2-hydroxy benzylidene and 1H-indol-3-ylmethylene hydrazides, a newer class of mosquito para-pheromones. We describe here synthesis of various novel long chain aliphatic acid (2-hydroxy benzylidene and 1H-indol-3-ylmethylene) hydrazides by conventional as well as microwave irradiation techniques.

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“…13 C NMR spectra were recorded on the same instrument at 100MHz using the same solvent and internal reference. Chemical shift is reported in δ (PPM).…”

Section: Experimental Generalmentioning

confidence: 99%

Synthesis, characterization and spectral studies of various newer long chain aliphatic acid (2-hydroxy benzylidene and 1H-indol-3-ylmethylene) hydrazides as mosquito para-pheromones

Awasthi¹,

Rishishwar²,

Rao³

et al. 2007

Journal of the Korean Chemical Society

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“…The feasibility of microwave-assisted synthesis has been demonstrated in various transformations like protection and deprotection 1 , condensation 2 , cycloaddition 3 , alkylation 4 , oxidation 5 , reduction 6 , synthesis of various heterocyclic compounds [7][8][9] , and in many other chemical reactions. The salient features of these transformations are the enhanced reaction rates, greater selectivity, and the experimental ease of manipulation 10 leading to an efficient, environment-friendly and cost-effective pathway to several synthetically useful compounds.…”

Section: Introductionmentioning

confidence: 99%

Rapid Solvent-free Synthesis of Aromatic Hydrazidesunder Microwave Irradiation

Jain

Gupta

Ganesan

et al. 2007

DSJ

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“…When the triene was heated in a sealed glass vessel in a modified microwave oven the adduct was obtained in 92 % yield. The same author used this strategy to synthesize tricyclic taxoid skeletons 55, an intramolecular Diels±Alder approach that proceeds in the direction from left to right (ring A to BC) (Scheme 9.14) [56]. Once again, microwave irradiation was necessary to perform the required cycloaddition in good yield.…”

Section: Diels±alder Reactionsmentioning

confidence: 99%

Microwaves in Cycloadditions

Hoz

Díaz‐Ortiz

Langa³

2002

Microwaves in Organic Synthesis

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The first examples of microwave-induced reactions were cycloadditions and pericyclic reactions performed under pressure, because of the use of domestic ovens, to avoid the risk of igniting flammable solvents (Scheme 9.1) [11,12].Reactions were performed in sealed thick-walled glass tubes or in Teflon acid-digestion vessels, in domestic microwave ovens [13]. Teflon vessels can be used at pressures up to 14 atm, at temperatures below 250 8C, and are resistant to most commonly used chemicals, although they deform at temperatures >250 8C.The lack of temperature and pressure control in these systems could lead to safety problems, because of overpressure resulting from the heating rate caused by microwaves. These problems can be reduced by using solvent-free methodology, which also enables the use of larger quantities of reagents. Yields have been greatly improved, and reaction times reduced, in comparison with conventional procedures in solvents under reflux.These reactions were next revisited by Strauss and it was shown that, under identical conditions in xylene, the reaction rates were strictly identical within experimental error [14]. Reactions under RefluxReactions involving a solvent under reflux require the use of modified commercial microwave ovens. In these modified systems the oven is perforated on the top to accommodate a reflux condenser and a 10 cm pipe is used to avoid microwave leakage; the turnable dish is replaced by a magnetic stirrer or by monomode reactors especially designed for chemical synthesis [15].The advantage of reactions involving solvent is that the reaction temperature is controlled by the reflux temperature of the solvent [16]. It should, however, be re-296 9 Microwaves in Cycloadditions CO 2 Me MeO 2 C MeO 2 C CO 2 Me MICROWAVE 10 min p-xylene, 87% 325º<361 ºC CONTROL 4 h p-xylene, 67% 138 ºC 1 2 3 Scheme 9.1 297 9.3 Solvent-free Conditions 5 6 7 8 Scheme 9.2 silica gel [29] and alumina [30]have also been used to generate 1,3-dipoles and, in this way, heterocyclic compounds can be obtained in a one-pot procedure. In these reactions changes in the regioselectivity of the reaction have not been observed under the action of microwave irradiation. Reactions without SupportAn alternative to the use of supported reagents is the use of uncatalyzed ªneat reactionsº. Under these conditions the radiation is absorbed directly by the reagents and this results in spectacular acceleration, higher yields and purity of the reaction products, a simple workup procedure, and sometimes changes in the selectivity of the cycloaddition. Diels±Alder reactions [31] and 1,3-dipolar cycloadditions [32,33] have been performed by use of this methodology. For example, DÌaz-Ortiz described the hetero-Diels±Alder and 1,3-dipolar cycloaddition reactions of ketene acetals. The reactions were improved and products were isolated directly from the crude reaction mixture without polymerization of the ketene acetals [34].When the enantiomerically pure ketene acetal 16 was used, cycloaddition with N,a-diphenylnitrone (11) or ...

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A cycloaddition approach to tricyclic taxoid skeletons

Cited by 20 publications

References 22 publications

Synthesis, characterization and spectral studies of various newer long chain aliphatic acid (2-hydroxy benzylidene and 1H-indol-3-ylmethylene) hydrazides as mosquito para-pheromones

Synthesis, characterization and spectral studies of various newer long chain aliphatic acid (2-hydroxy benzylidene and 1H-indol-3-ylmethylene) hydrazides as mosquito para-pheromones

Rapid Solvent-free Synthesis of Aromatic Hydrazidesunder Microwave Irradiation

Microwaves in Cycloadditions

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