Regioselective synthesis of flavone derivatives via DMAP-catalyzed cyclization of o-alkynoylphenols

A catalytic amount of DMAP promoted cyclization of o-alkynoylphenols via a 6-endo cyclization mode leading to flavone derivatives in high yields without forming 5-exo cyclized aurone derivatives. Utilizing this method, methoxy substituted flavone and alkyl substituted γ-benzopyranone derivatives were synthesized.     

Palladium‐ and Solvent‐Free Synthesis of Ynones by Copper(I)‐Catalyzed Acylation of Terminal Alkynes with Acyl Chlorides under Aerobic Conditions

Air‐stable Cu^I/cryptand‐22 complex was found to be a highly active catalyst for the solvent‐free cross‐coupling reaction of terminal alkynes with different acyl chlorides in the presence of Et₃N as base to give the corresponding ynones in quantitative yields.     

Synthesis and comparative study of catalytic activity between Pd-metallodendrimer and Pd/Cu-bimetallodendrimer nanoparticle-based on triazine

Triazine-based heterogeneous Pd/Cu-bimetallodendrimer Nanoparticle (Pd/Cu-BMDNP) has been synthesized by sequential loading method from palladium containing metallodendrimer (Pd-MD) which was prepared by the reaction of 2,4,6-Triamine-1,3,5-triazine (melamine) with substituted benzoyl chloride using (Ph₃P)₂PdCl₂ in DMSO at 90 °C. SEM and EDX of Pd/Cu-BMDNP showed the nanosized aggregated spherical surface morphology and the presence of Palladium and copper of the NP. Also, the phase was detected as Face Centered Cubic (FCC) structure by XRD analysis. In addition, the average particle size of Pd/Cu bimetallic catalyst was identified as 12–13 nm by TEM investigation. Greater thermal stability of Pd/Cu-BMDNP than Pd-MD was detected from TG and DSC experiments. The Pd-metallodendrimer has been also characterized by IR, ¹H NMR, ¹³C NMR, SEM, EDX, Mass, TG and DSC techniques. The simple recoverability, high reusability, low amount of catalyst loading, negligible amount of catalyst leaching of the heterogeneous Pd/Cu-BMDNP have made more effective catalyst than homogeneous Pd-metallodendrimer for the C–C cross-coupling reaction such as Heck, Glaser, Sonogashira and Suzuki-Miyaura in excellent yields.     

Facile and efficient addition of terminal alkynes to benzotriazole esters: synthesis of d-erythro-sphingosine using ynones as the key intermediate

From the perspective of synthesis, ynones are compounds of considerable interest because of their occurrence in a wide variety of biologically active molecules and as key synthetic intermediates. In this context, a facile and highly efficient synthesis of ynones was developed based on the high reactivity of benzotriazole esters formed in situ. Lithium acetylides can alkylate various carboxylic acids in yields ranging from 60% to 92%. To determine whether our methodology is useful for synthesising complex and biologically relevant molecules, we synthesise d-erythro-sphingosine in four steps and with 33% overall yield from l-serine.     

Synthesis of 3-carbonyl pyrazole-5-phosphonates via 1,3-dipolar cycloaddition of Bestmann–Ohira reagent with ynones

The present work explores the hitherto unexplored reactivity of ynones as dipolarophiles with Bestmann–Ohira reagent. The reaction offers a convenient route for the synthesis of regioisomerically pure 3,5-disubstituted or 3,4,5-trisubstituted pyrazoles in excellent yields. However, di-ynones and molecules possessing both ynone and enone functionalities provide only monocycloaddition products, whereas another multiple bond undergoes Michael addition with the methoxide anion.     

Solvent free synthesis of ynones using magnetically recoverable Copper-ferrite nanoparticles

A general and efficient biogenic CuFe₂O₄ MNP’s catalyzed synthesis of ynones has been reported for the first time. The reaction occurs in solvent free conditions without the use of any harsh conditions. The average diameter of the nanoparticles was found to be 13.07 nm. The advantages of the protocol include heterogeneous catalysis, easy recyclability of the catalyst and short reaction time.     

Complementary regioselective synthesis of 3,5-disubstituted isoxazoles from ynones

Two regioselective synthetic routes towards 3,5-disubstituted isoxazoles from ynones are reported. One route takes place via first converting the ynones to ynone O-methyl oximes, followed by a palladium-catalyzed intramolecular cyclization. The other involves the formation of 5-hydroxy-4,5-dihydroisoxazoles by a cyclocondensation between ynones and hydroxylamine, and subsequent acid mediated dehydration. The two routes are not only both highly regioselective, but also complementary to each other as a pair of regioisomeric 3,5-disubstituted isoxazoles are readily prepared from one single ynone substrate. The efficiency of the two routes are further evaluated and demonstrated in the synthesis of three representative 3,5-disubstituted isoxazoles.     

Cu0-catalysed 1,3-dipolar cycloadditions of α-amino acid derived N,N-cyclic azomethine imines to ynones

A series of 20 CuAIAC reactions between eight 4-acylamino substituted pyrazolidine-3-one-1-azomethine imines and four terminal ynones were performed using Cu⁰ as catalyst. The corresponding fluorescent cycloadducts were obtained in very high yields upon simple workup. Thus, Cu-metal turned out to be a better catalyst than Cu^I in terms of yield and ease of isolation. Availability of azomethine imines, mild reaction conditions, and simple workup enable a “click” access to libraries of densely substituted 2,3-dihydro-1H,5H-pyrazolo[1,2-a]pyrazol-1-ones. Reactivity of differently substituted dipoles was evaluated experimentally and by quantum chemical methods (DFT).     

Using Pd-salen complex as an efficient catalyst for the copper-and solvent-free coupling of acyl chlorides with terminal alkynes under aerobic conditions

<正>The palladium-salen complex palladium(Ⅱ) N,N'-bis{[5-(triphenylphosphonium)-methyl]salicylidene}-1,2-ethanediamine chloride was found to be a highly active catalyst for the copper- and solvent-free coupling reaction of terminal alkynes with different acyl chlorides in the presence of triethylamine as base,giving excellent ynones under aerobic conditions.