Rh(III)-catalyzed C–H acylmethylation of 2H-indazoles with sulfoxonium ylides

An efficient Cp*Rh(III)-catalyzed direct acylmethylation of 2H-indazoles with sulfoxonium ylides has been realized under air atmosphere via chelation-assisted strategy. This protocol enables a regioselective access to a variety of ortho-acylmethylated 2-phenylindazole derivatives in moderate to good yield, which has the advantages of broad substrate scope, good functional group tolerance, and operational convenience. The H/D exchange experiment reveals that a reversible cleavage of C–H bond might not be the rate-limiting step in this transformation.     

Rh(III)-catalyzed [4 + 1]-annulation of azobenzenes with α- carbonyl sulfoxonium ylides toward 3-acyl-(2H)-indazoles

A Rh(III)-catalyzed [4?+?1]-annulation of azobenzenes with α- carbonyl sulfoxonium ylides was developed to access 2H-indazoles in moderate to excellent yields with good functional group compatibilities. It proceeded with the sequential insertion of the Rh(III) carbene to the C?H bond and cyclization steps, where sulfoxonium ylides served as efficient and stable carbene precursor.     

Gold(III)-catalyzed tandem conjugate addition/annulation of 4-hydroxycoumarins with α,β-unsaturated ketones

An efficient and selective approach for the synthesis of functionalized pyranocoumarins has been developed via a gold(III)-catalyzed tandem conjugate addition/annulation reaction of 4-hydroxycoumarins with α,β-unsaturated ketones.     

Au(III)-catalyzed tandem amination-hydration of alkynes: synthesis of α-(N-2-pyridonyl)ketones

A new Au(III)-catalyzed tandem amination-hydration reaction has been discovered, leading to the formation of α-(N-2-pyridonyl)ketones and heterocyclic analogues in good to excellent yields (14 examples, 48-90%). This reaction demonstrates the unusual use of a heterocyclic sp(2) nitrogen nucleophile in a gold-catalyzed 6-endo-dig cyclization. The tandem process allows rapid access to α-(N-2-pyridonyl)ketones, making them a convenient building block for the synthesis of more complex N-alkyl pyridone targets.     

Cu(I)-catalyzed α-alkylation of ketones with styrene derivatives

α-Alkylation of ketones with styrene derivatives was developed using a mesitylcopper-dppp complex as a soft Brønsted base catalyst. No waste derived from the alkylating reagent was produced in this catalytic alkylation reaction. The bisphosphine ligand structure, as well as the reaction solvent, had profound effects on catalyst activity. The reaction proceeded under mild conditions from a range of ketones and styrene derivatives. The present catalysis is especially useful for the selective mono-alkylation of ketones.     

Sc(III)-catalyzed enantioselective addition of thiols to α,β-unsaturated ketones in neutral water

This report concerns Lewis acid catalyzed enantioselective sulfa-Michael addition in neutral water by using a very efficient Sc(OTf)(3)/bipyridine 1 catalytic system. It is noteworthy that the protocol presented employs water as a reaction medium and allows us to obtain very high stereoselectivity and satisfactory yields for β-keto sulphides deriving from aliphatic thiols. The recovery and reuse of both the aqueous medium and the catalytic system is also reported.     

Facile and efficient preparation of α-halomethyl ketones from α-diazo ketones catalyzed by iron(III) halides and silica gel

An efficient and mild method for the synthesis of α-halomethyl ketones from α-diazo ketones was developed using ferric chloride or bromide as the halogen source and silica gel as the hydrogen source, with good to excellent yields.     

(NMCp)2TiCl2-catalyzed reduction of aliphatic,aromatic and α,β-unsaturated ketones by grignard reagent

Aliphatic, aromatic and α,β-unsaturated ketones were readily reduced to the corresponding secondary alcohols by iso-propylmagnesium bromide in the presence of a catalytic amount of bis(neomenthylcyclopentadienyl)titanium dichloride. A possible mechanism is discussed.     

Magnetically recyclable Cu-BTC@Fe3O4-catalyzed synthesis of aryl α-chlorobenzyl ketones

Metal–organic framework (MOF) composite, viz. Cu-BTC@Fe₃O₄ (BTC is 1,3,5-benzenetricarboxylate), was prepared and utilized for the synthesis of aryl α-chlorobenzyl ketones from arenediazonium salts and arylacetylenes in moderate to good yields. This reaction proceeded via a radical domino process. The catalyst could be readily recovered with an external permanent magnet, with slight decrease in its activity after successive six runs.     

An efficient Fe(III)-catalyzed 1,6-conjugate addition of para-quinone methides with fluorinated silyl enol ethers toward β,β-diaryl α-fluorinated ketones

Reported here is a highly efficient 1,6-conjugate addition of fluorinated silyl enol ethers to para-quinone methides, allowing facile access to a range of β,β-diaryl α-fluorinated ketones with good to high yields. Fe(OTf)₃ was identified as the optimal catalyst, with the loading of 3?mol%. Notably, this represent the first 1,6-conjugate addition with fluorinated silyl enol ethers. The synthetic potential of the resulting adducts is also demonstrated.     

Direct synthesis of benzoxazinones via Cp*Co(III)-catalyzed C–H activation and annulation of sulfoxonium ylides with dioxazolones

A highly novel and direct synthesis of benzoxazinones was developed via Cp*Co(III)-catalyzed C–H activation and [3 + 3] annulation between sulfoxonium ylides and dioxazolones. The reaction is conducted under base-free conditions and tolerates various functional groups. Starting from diverse readily available sulfoxonium ylides and dioxazolones, a variety of benzoxazinones could be synthesized in one step in 32%-75% yields.     

Efficient one-pot synthesis of α-aminophosphonates from aldehydes and ketones catalyzed by ytterbium(III) triflate

An efficient three component one-pot synthesis of N-silylated α-aminophosphonates and α,α-disubstituted α-aminophosphonates was developed using Yb(OTf)₃ as a catalyst at room temperature under mild conditions.     

An efficient heterogeneous gold(I)-catalyzed hydration of haloalkynes leading to α-halomethyl ketones

A highly efficient heterogeneous gold(I)-catalyzed hydration of haloalkynes has been developed that proceeds smoothly under mild and neutral conditions and provides a general and practical route for the synthesis of a variety of α-halomethyl ketones with high atom-economy, excellent yield, and recyclability of the gold(I) catalyst. The presented method delivers an attractive alternative to classical α-halogenation of ketones.     

Rh(Ⅰ)-catalyzed borylation of primary alkyl chlorides

Rhodium-catalyzed cross-coupling reactions of unactivated primary alkyl chlorides with diboron reagents have been developed as practical methods for the synthesis of alkylboronic esters. These reactions expand the concept and utility of Rh(I)-catalyzed cross-coupling of aliphatic electrophiles.     

A practical synthesis of 3-acyl cyclobutanones by [2 + 2] annulation. Mechanism and utility of the Zn(II)-catalyzed condensation of α-chloroenamines with electron-deficient alkenes

New conditions for the conversion of simple tertiary amides to α-chloroenamines and their use in Zn(II)-catalyzed cycloaddition reactions with commercial α,β-unsaturated carbonyl compounds allows rapid, regiocontrolled access to 3-acyl cyclobutanones. Reactions take place at ambient temperature without solvent, giving strained [2 + 2] adducts with all-carbon-substituted quaternary carbon atoms. Ab initio calculations of the putative keteniminium intermediate and studies with styrenyl olefins suggest a dual role for Zn(OTf)(2) during catalysis.     

Synthesis of indoles through Rh(III)-catalyzed C–H cross-coupling with allyl carbonates

A practical Rh-catalyzed reaction was developed to achieve 2-alkyl-substituted indole synthesis. The reaction can tolerate a variety of synthetically important functional groups. The indole products can also be transformed into other important skeletons. Two bioactive compounds, that is indomethacin and pravadoline were prepared using the new method.     

Ga(ClO4)3-catalyzed synthesis of quinoxalines by cycloaddition of α-hydroxyketones and o-phenylenediamines

A new approach for the synthesis of 2-substituted quinoxalines by Ga(ClO₄)₃-catalyzed cycloaddition of α-hydroxyketones and o-phenylenediamines is introduced. The reaction is catalyzed by 10 mol % of Ga(ClO₄)₃ in EtOH at room temperature. It is performed under simple and mild conditions to afford the product in good yield.     

Rh2(CO)4(μ-Cl)2和Rh4(μ-CO)3(CO)4的简正振动分析

金属簇合物具有独特的结构和成键方式。本文对铑簇合物的简正振动分析进行了研究。通过红外光谱用石蜡油糊涂KBr和聚乙烯窗口, 在Nicolet 200SXV FT-IR光谱上测定了Rh2(CO)4(μ-Cl)2的构型, 并使用分子振动全分析程序MVTA(Basic语言), 在PC机上进行计算。