21421-66-9Relevant academic research and scientific papers
Scope and Mechanism of the Ruthenium-Catalyzed Dehydrative C-H Coupling of Phenols with α,β-Unsaturated Carbonyl Compounds: Expedient Synthesis of Chromene and Benzoxacyclic Derivatives
Mokar, Bhanudas Dattatray,Yi, Chae S.
supporting information, p. 4625 - 4632 (2019/12/24)
Chromene and benzoxacyclic derivatives were efficiently synthesized from the ruthenium-catalyzed dehydrative C-H coupling reaction of phenols with α,β-unsaturated carbonyl compounds. The cationic ruthenium-hydride complex was found to be an effective catalyst for the coupling and annulation of phenols with enals to form chromene products. The coupling of phenols with linear enones afforded 2,4-disubstituted chromene derivatives, whereas the analogous coupling with cyclic enones yielded 9-hydroxybenzoxazole products. The reaction of 3,5-dimethoxyphenol with PhCH=CHCDO resulted in the chromene product with a significant H/D exchange to both benzylic and vinyl positions. The most significant carbon isotope effect from the coupling of 3,5-dimethoxyphenol with 4-methoxycinnamaldehyde was observed on the α-olefinic carbon of the chromene product (C(2) = 1.067). A Hammett plot from the coupling of 3,5-dimethoxyphenol with para-substituted p-X-C6H4CH=CHCHO displayed a linear correlation, with a strong promotional effect by an electron-withdrawing group (ρ = +1.5; X = OCH3, CH3, H, F, Cl). Several biologically active chromenone derivatives were synthesized by using the catalytic coupling method. The catalytic method provides an expedient synthetic protocol for the coupling of phenols with α,β-unsaturated carbonyl compounds without employing reactive reagents or forming any wasteful byproducts.
Boronic acid/Br?nsted acid co-catalyst systems for the synthesis of 2: H -chromenes from phenols and α,β-unsaturated carbonyls
Dimakos, Victoria,Singh, Tishaan,Taylor, Mark S.
, p. 6703 - 6711 (2016/07/21)
Protocols for the synthesis of substituted 2H-chromenes from α,β-unsaturated carbonyls and phenols are described. Optimal combinations of arylboronic acids and Br?nsted acids have been identified, such that both can be employed in catalytic quantities to accelerate these condensations. The method has been used to synthesize a variety of substituted 2H-chromenes, as well as photochromic naphthopyrans. The use of pentafluorophenylboronic acid and diphenylphosphinic acid enabled an expansion of the electrophile scope to include α,β-unsaturated ketones. Hall's 'phase-switching' of boronic acids has been exploited to achieve the separation of the two co-catalysts from unpurified reaction mixtures by a simple liquid-liquid extraction.
Natural product-like combinatorial libraries based on privileged structures. 1. General principles and solid-phase synthesis of benzopyrans
Nicolaou,Pfefferkorn,Roecker,Cao,Barluenga,Mitchell
, p. 9939 - 9953 (2007/10/03)
Herein we report a novel strategy for the design and construction of natural and natural product-like libraries based on the principle of privileged structures, a term originally introduced to describe structural motifs capable of interacting with a variety of unrelated molecular targets. The identification of such privileged structures in natural products is discussed, and subsequently the 2,2-dimethylbenzopyran moiety is selected as an inaugural template for the construction of natural product-like libraries via this strategy. Initially, a novel solid-phase synthesis of the benzopyran motif is developed employing a unique cycloloading strategy that relies on the use of a new, polystyrene-based selenenyl bromide resin. Once the loading, elaboration, and cleavage of these benzopyrans was established, this new solid-phase method was then thoroughly validated through the construction of six focused combinatorial libraries designed around natural and designed molecules of recent biological interest.
A Novel Synthesis of Precocenes. Efficient Synthesis and Regioselective O-Alkylation of Dihydroxy-2,2-dimethyl-4-chromanones
Timar, Tibor,Jaszberenyi, J. Csaba
, p. 871 - 877 (2007/10/02)
The reactions of trihydroxybenzenes 1a-c and 3-methylbut-2-enoic acid (2) in a zinc chloride/water/phosphoryl chloride system afford either the new trihydroxyphenylbutenone derivatives 3b,c or dihydroxy-2,2-dimethyl-4-chromanones 4a-c in good yields.Compounds 3b,c can be cyclized in high yields to 4b,c in 5percent sodium hydroxide solution.Regioselective O-alkylation of 4a-c leads to 5a-f in good yields.O-Alkylation of 5a-f, followed by reduction and dehydration, results in the formation of precocene 3 (7d) and its regioisomer 7a-c,e,f.Methylation of 4a-c gives 6g-i.Subsequent reduction and dehydration affords precocene 2 (7h) and its regiosiomers 7g,i.
A New Preparative Method of 2,2-Dimethyl-2H-chromenes
Kawase, Yoshiyuki,Yamaguchi, Seiji,Horita, Hisanori,Takeno, Junko,Kameyama, Hideaki
, p. 1153 - 1155 (2007/10/02)
2,2-Dimethyl-2H-chromene was prepared from salicylaldehyde and ethyl 3-methyl-2-butenoate (or ethyl α-bromoisobutyrate) in one step.This new method of preparing 2,2-dimethyl-2H-chromene was studied and applied to some 2,2-dimethyl-2H-chromene derivatives.
A CONVENIENT SYNTHESIS OF 2,2-DIMETHYLCHROMENES FROM 2,2-DIMETHYLCHROMANONES
Tsukayama, Masao,Sakamoto, Tsukasa,Horie, Tokunaru,Masamura, Mitsuo,Nakayama, Mitsuru
, p. 955 - 958 (2007/10/02)
2,2-Dimethylchromanones were very easily reduced to the corresponding alcohols by sodium borohydride-palladium chloride, and the alcohols were converted into the corresponding 2,2-dimethylchromenes by dehydration with potassium hydrogensulfate in high yields based on 2,2-dimethylchromanones
RUTACEOUS CONSTITUENTS-13 A BIOMIMETIC SYNTHESIS OF ACRONYCINE
Adams, Joyce H.,Brown, P. Margaret,Gupta, Padma,Khan, M. Shafig,Lewis, John R.
, p. 209 - 218 (2007/10/02)
A biomimetic synthesis of the anti-tumor active alkaloid acronycine (7; R=R'=Me) has been obtained by cyclisation of 6-(2-methylaminobenzoyl)-5,7-dimethoxy-2,2-dimethylchromene (11; R=R'=Me); isoacronycine (20; R=R'=Me) was also produced.In an analogous manner the aminochromene (11; R=H, R'=Me) gave a mixture of des-N-methylacronycine (7; R=H, R'=Me) and des-N-methylisoacronycine (20; R=H, R'=Me).The aminochromenes were best synthesised by condensation of lithio-5,7-dimethoxy-2,2-dimethylchromene (22; R=Li) with N-methylisatoic anhydride (26) or with 2-methyl-3,1-benzoxazin-4-one (21).The relevance of this synthetic route to the biogenesis of acridone alkaloids is discussed.
