Prenyl Ethers Research Articles

ChemInform Abstract: Highly Selective Cleavage of Prenyl Ethers by Means of a TiCl4‐n‐Bu4NI Mixed Reagent.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Highly selective cleavage of prenyl ethers by means of a TiCl 4- n-Bu 4NI mixed reagent

Treatment of the prenyl ether of salicylate with a TiCl 4- n-Bu 4NI mixed reagent resulted in cleavage of the CO bond to provide ethyl salicylate in quantitative yield. On the other hand, no cleavage reaction was observed when ethyl p-prenyloxybenzoate was used as a substrate. In this system, the cleavage reaction of ethers proved to be accelerated by the chelating effect of a neighboring group in the substrate.

ChemInform Abstract: Sparteine‐Mediated Enantioselective [2,3]‐Wittig Rearrangement of Allyl ortho‐Substituted Benzyl Ethers and ortho‐Substituted Benzyl Prenyl Ethers.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform Abstract: A Mild and Highly Selective Deprotective Method of Prenyl Ethers Using Ytterbium Triflate.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Sparteine-mediated enantioselective [2,3]-Wittig rearrangement of allyl ortho-substituted benzyl ethers and ortho-substituted benzyl prenyl ethers

The (−)-sparteine-mediated enantioselective [2,3]-Wittig rearrangement of N, N-dialkyl- o-allyloxymethylbenzamides and o-substituted benzyl prenyl ethers has been investigated. Enantiomeric excess up to 60% was observed as for the reaction with N, N-diethyl- o-allyloxymetylbenzamide. From the mechanistic investigations, it was suggested that the stereoinformation was introduced at the deprotonation step. Substoichiometric amount of (−)-sparteine (0.2 equiv.) did not decrease the enantioselectivity. Introduction of functional groups other than carbamoyl group did not enhance the enantioselectivity in this rearrangement.

ChemInform Abstract: Enantioselective [2,3]‐Wittig Rearrangement via Sparteine‐Mediated Lateral Metalation of N,N‐Dialkyl‐o‐allyloxymethylbenzamides and o‐Substituted Benzyl Prenyl Ethers.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Enantioselective [2,3]-Wittig Rearrangement via Sparteine-Mediated Lateral Metalation of N,N-Dialkyl-o-allyloxymethylbenzamides and o-Substituted Benzyl Prenyl Ethers

The (-)-sparteine-mediated enantioselective [2,3]-Wittig rearrangement of N,N-dialkyl-o-allyloxymethylbenzamides and o-substituted benzyl prenyl ethers has been investigated. With N,N-diethyl-o-allyloxymethylbenzamide, enantiomeric excess up to 60% was observed in pentane. These results suggest that the carbamoyl group can effectively assist the transfer of stereoinformation by coordinating with the (-)-sparteine-n-BuLi complex. Other functional groups (OMe, OCONR2, OMOM, F) were impotent to the enantiodifferentiation of this rearrangement.

A Mild and Highly Selective Deprotective Method of Prenyl Ethers Using Ytterbium Triflate

A Mild and Highly Selective Deprotective Method of Prenyl Ethers Using Ytterbium Triflate

Nahocols and isonahocols, endothelin antagonists from the brown alga, sargassum autumnale

Novel endothelin antagonists, nahocols A, A1, B, C, D1 and D2, and isonahocols D1 and D2, were isolated from the brown alga, Sargassum autumnale. Their structures were determined through detailed analysis of NMR spectra and chemical reactions. Nahocols have an aryl prenyl ether structure, which are speculated to be biogenetic precursors of the ubiquitous prenyl hydroquinones or prenyl benzoquinones in the plant and animal kingdoms.

ChemInform Abstract: Facile Synthesis of 2,2‐Dimethylchromans by Mo(CO)6‐Catalyzed Reaction of Aryl Prenyl Ethers.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Facile Synthesis of 2,2-Dimethylchromans by Mo(CO)6 Catalyzed Reaction of Aryl Prenyl Ethers

Facile Synthesis of 2,2-Dimethylchromans by Mo(CO)6 Catalyzed Reaction of Aryl Prenyl Ethers

Claisen rearrangement of prenyl ethers of isomeric acetylnaphthols and bisprenyl ethers of 4,6- and 2,4-diacetylresorcinols

Claisen rearrangements of the 3-methylbut-2-enyl(prenyl) ethers 3 and 9 of 2-acetyl-1-hydroxyand 1-acetyl-2-hydroxynaphthalenes 1 and 2 and the bis(3-methylbut-2-enyl) ethers 12 and 18 of 2,4-and 4,6-diacetylresorcinols 11 and 17 have been studied under a variety of thermal and catalytic conditions. 2-Acetyl-4-(3- methylbut-2-enyl) naphthalene-1-ol 4 was the sole product on rearrangement of compound 3, in DMA or neat. Under catalytic conditions 3,4-dihydro-2,2-dimethyl-2H-naphtho[1,2-b]pyran 7 was obtained in poor yield. An isomeric pyran, 1,2-dihydro-3,3-dimethyl-3H-naphtho[2,1-b]pyran 10(25–43%) was obtained under both thermal and catalytic conditions from 9. The rearrangement of 12 under thermal conditions (DMA and neat) furnished 3-acetyl-2,4-dihydroxy5-(3-methylbut-2-enyl)acetophenone 13 and 3,8-diisopropylbenzo[1,2-b: 3,4-b′]difuran 14. PdII mediated rearrangement of 12 gave only the partially deprenylated ether, 3-acetyl-4-hydroxy-2-(3-methylbut-2-enyloxy)acetophenone 15(29%). While the isomeric ether 18 gave the monoprenyl ether, 5-acetyl-4-hydroxy-2-(3-methylbut-2-enyloxy)acetophenone 19 in quantitative yield (95%). The rearrangement products were characterised and their formation rationalised in terms of allowed sigmatropic shifts ([3,3] prenyl and [1,5] H) followed by loss of prenyl or acetyl groups. The reactions of prenyl ethers are both comparable to those of the corresponding allyl ethers and consistent with the greater fixed double-bond character of the naphthalene system compared to that of benzene. Prenyl derivatives of benzene and naphthalene containing ortho-hydroxyacetophenone units were formed which have potential in synthesis.

Synthesis of Terpenoids such as Geraniol and Farnesol by Cross Coupling Reactions

The ene-type chlorination of benzyl prenyl ether (1 a) and benzyl geranyl ether (1 b) with hypochlorous acid gave allylic chlorides (2) in good yields. Allylic chlorides (2) reacted with Grignard reagents such as isoamylmagnesium bromide (2 a) and n-butylmagnesium bromide (2 b) in the presence of CuCl to give γ-ross coupling products (5) and (6) in high regioselectivities. Reactions of allylic chlorides (2) with prenylmagnesium chloride (2 c) were subsequently conducted in the presence of CuI to obtain the cross coupling products (4), (5) and (6).

Claisen rearrangements—VI : Synthesis of the coumarins, sesibiricin and toddaculin

The natural coumarins, sesibiricin ( 1) and toddaculin ( 28) have been synthesised from 5,7-dihydroxycoumarin, the former by a sequence involving regioselective O-prenylation at C-5 and C-prenylation at C-8. The prenyl ether of 5-hydroxy-7-methoxycoumarin, a key intermediate in the synthesis of toddaculin, has been found to undergo Claisen rearrangement exclusively to the para position thereby providing an alternative route to sesibiricin.

ChemInform Abstract: SYNTHESIS OF (+‐)‐7,3′‐ AND 7,4′‐DI‐O‐METHYLERIODICTYOL AND OF VELUTIN AND PILLOIN

AbstractAusgehend von 2′‐Hydroxy‐3,4′,6′‐trimethoxy‐4‐benzyloxychalkon (I) wird durch Behandlung mit Bromwasserstoffsäure in Eisessig in 30%iger Ausheute (i)‐7,3′‐Di‐O‐methyleriodictyol (II) dargestellt, das mit racemisiertem natürlichem Produkt identisch ist.

Synthesis of (±)-7,3′- and 7,4′-di- O-methyleriodictyol and of velutin and pilloin

Synthetic 2′-hydroxy-3,4′,6′-trimethoxy-4-benzyloxychalcone (I) affords (±)-7,3′-di- O-methyleriodictyol (II) and 7,3′-di- O-methylluteolin (or velutin, VII) identical with natural samples. Similarly synthetic 2′-hydroxy-4,4′,6′-trimethoxy-3-benzyloxychalcone (X) gives natural (±)-7,4′-di- O-methyleriodictyol (XI) and 7,4′-di- O-methylluteolin (or pilloin, IX). However, attempts to partially etherify II with one mole of prenyl bromide to obtain the natural prenyl ether failed; only the corresponding diprenyloxychalcone (IV) was obtained.