New Pathways for Organic Synthesis

Colquhoun, Howard M.; Holton, J.; Thompson, D. J.; Twigg, M. V.

doi:10.1007/978-1-4613-2651-9

Cited by 95 publications

(21 citation statements)

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“…Et,O 1121 under mild conditions left 1 unchanged. Transitionmetal complexes were not assayed owing to presumably [13] harsh conditions for 1. We, therefore, envisaged to transpose the double bond into the conjugated position via oxygenation/P-elimination.…”

Section: ')mentioning

confidence: 99%

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New Furano‐sesquiterpenoids from Mediterranean Sponges

Guella

Mancini

Guerriero

et al. 1985

Helvetica Chimica Acta

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A mixture of sponges of the East Pyrenean Mediterranean is shown to contain the known sponge products longifolin (I), avarol ((+)-3), and avarone (4) and the terrestrial-plant product sesquirosefuran (2), besides to the new furano-sesquiterpenoids tavacfuran ( = 3-methyl-2-[(3'Z)-3'-methyl-rl'-(4"-methyl-2"-furyl)-3'-butenyl]furan ; 5) and tavacpallescensin ( = 5,l0-dihydro-6,9-dimethyl-4H-benzo[5,6]cyclohepta[1,2-~]furan; 6) and the new fu- rano-butenolide sesquiterpenoids tavacbutenolide-1 ( = (&)-4-ethoxy-2-methyl-4-[(2'E)-2'-methyl-4'-(3"-methyl-2"-furyl)-2'-butenyi]-2-buten-4-olide; (*)-7) and tavacbutenolide-2 ( = (&)-4-ethoxy-3-methy1-4-[(2'E)-3'-methyl-4'-(4"-methyl-2"-furyl)-2'-butenyl]-2-buten-4-olide ; (&)-8).Structural assignments are based on NMR data and on the synthesis of the (E)-isomer of 5. The sponge Dysidea tuphu of the same area is also shown to contain the two sesquiterpenoids mt-furodysinin ((-)-14), which is enantiomeric to a product of a Dysidea sp. of Australian waters, and tuphabutenolide ((+)-15). Results andDiscussion. -Our mixture of sponges proved to contain the two known linear furano-sesquiterpenoids longifolin (1) and sesquirosefuran (2) and the two known rearranged drimanes avarol ((+)-3) and avarone (4) of mixed biogenesis. Compounds 3 and 4 have been previously isolated from a non-better described Mediterranean [8] collection of D. avara, whereas 1 was initially isolated from the terrestrial Japanese plant Actinodaphne longifolia (BLUME) (which also contains 2 [9]) and later from either the marine sponge Pleraplysilla spinifera [3a] and the nudibranch Glossodoris gracilis [3b].Our mixture of sponges proved also to contain the new furano-sesquiterpenoids 5 and 6 and the new furano-butenolide sesquiterpenoids 7 and 8. The isomer 5 of longifolin, which is named 'tavacfuran' from the place of collection of our sponge mixture, is

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Section: ')mentioning

confidence: 99%

“…phase washed with H20, dried, and evaporated, and the residue (0.035 g) subjected to reverse-phase HPLC with CH,CN/H,O 82:18 to give, in roughly equal amounts, first 1, followed, in the given order, by an uninvestigated product, 13, and 5. This sample of 13 was further subjected to HPLC to give 0.004 g of pure 3 13. Colourless oil.…”

Section: Auarol((+)-3)mentioning

confidence: 99%

New Furano‐sesquiterpenoids from Mediterranean Sponges

Guella

Mancini

Guerriero

et al. 1985

Helvetica Chimica Acta

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“…18 As shown above, the copper salt exerts a similar effect on the regioselectivity of reduction by the tita nium(III) ions. In the absence of iron compounds, the reduction of aromatic PNC using these methods affords mainly para isomers, 18,19 whereas the amount of ortho isomers increases sharply in the presence of iron hydroxide or iron salts.…”

Section: Resultsmentioning

confidence: 78%

Change in regioselectivity in the monoreduction of 2,4,6-trinitrotoluene with titanium(III) and vanadium(II) ions in the presence of iron(II) and copper(II) salts

et al. 2005

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Small additives of iron(II) or copper(II) salts change the regioselectivity of 2,4,6 trinitro toluene monoreduction with titanium(III) chloride affording predominantly less accessible 2 amino 4,6 dinitrotoluene over 4 amino 2,6 dinitrotoluene (from 25% when the reduction occurs in the absence of the iron and copper salts to 70% in the presence of these salts). A possible mechanism of the process is discussed.

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“…Bis(trichlorophosphine)dichloropalladium(II), bis-(tribenzylphosphine)dichloropalladium(II), and bis-(tributylphosphine)dichloropalladium(II) were synthesized as described in [12].…”

Section: Methodsmentioning

confidence: 99%

Development of methods of ligand control in Pd-catalyzed hydrosilylation of 1,3-alkadienes

Reznikov

Skvortsov

2004

Russ J Gen Chem

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The catalytic activity of palladium(II) complexes in trichlorosilane reactions with 1,3-alkadienes (isoprene and 2,3-dimethyl-1,3-butadiene) is strongly affected by the nature of the phosphorus-containing ligand.Among hydrosilylation catalysts, platinum and rhodium complexes are unquestionably the most important. Palladium complexes have scarcely been used in hydrosilylation reactions. However, the most considerable progress in the asymmetric hydrosilylation of alkenes and dienes is associated with the use of palladium catalysts [134]. In this connection we considered it of interest to explore the relationship between the structure of these complexes and their catalytic properties.2-Alkenylsilanes possess a powerful synthetic potential and can be used for tackling important problems of fine organic synthesis [5]. One of the simplest synthetic approaches to such compounds is provided by hydrosilylation of 1,3-alkadienes in the presence of palladium complexes, that occurs as 1,4-addition to form a Z isomer [638].At the same time, scarce and contradictory data are available on the effect of the ligand environment on the catalytic properties of palladium complexes in hydrosilylation reactions [8,9]. The proposed mechanism of hydrosilylation of conjugated dienes in the presence of palladium complexes, while having a number of common stages, strongly differs from that proposed by Tsuji et al. [8] for Pt-catalyzed hydrosilylation of unsaturated compounds [8]. The referees [8] considered possible a p-allyl complex as a key intermediate controlling the regioselectivity of the reaction. The similarity and dissimilarity of the possible mechanisms implies that there are certain common features and differences in the structure (ligand environment)3catalytic activity relationships for palladium and platinum complexes in hydrosilylation reactions [10]. Experimental evidence for the hydrosilylation mechanism can be obtained by studying reaction of transition metal complexes with hydrosilanes. Transformations of Pd(II) complexes under hydrosilylation conditions have only been explored by Tsuji et al. [8] who established that the reactions of [PdCl 2 (Ph 3 P) 2 ] and [Pd(Ph 3 P) 4 ] with trichlorosilane involve formation of [Pd(Ph 3 P) 2 ] as a true catalyst.We decided to focus again on similar objects and to trace transformations of the Pd(II) and Pt(II) complexes we studied previously in reactions with (1-cyclohexenyl)diphenylphosphine [11] directly in the hydrosilane medium by 31 P NMR spectroscopy. In our opinion, this method holds the greatest promise, since the phosphorus chemical shift and, especially, the J PtP coupling constant are quite sensitive to the valence state of the central atom and its ligand environment, as well as to the geometric structure of the complex. One more advantage of this method over 1 H NMR spectroscopy is that organic compounds (hydrosilanes) do not interfere with registering the spectra of the starting complex and reaction products.In a typical experiment, a weighed sample of catalyst was dissolv...

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New Pathways for Organic Synthesis

Cited by 95 publications

References 0 publications

New Furano‐sesquiterpenoids from Mediterranean Sponges

New Furano‐sesquiterpenoids from Mediterranean Sponges

Change in regioselectivity in the monoreduction of 2,4,6-trinitrotoluene with titanium(III) and vanadium(II) ions in the presence of iron(II) and copper(II) salts

Development of methods of ligand control in Pd-catalyzed hydrosilylation of 1,3-alkadienes

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