Cross-dehydrogenative coupling of secondary benzylic ethers with indoles and pyrroles

Current studies on cross-dehydrogenative coupling of benzylic ethers for new C–C bond construction predominantly focus on primary ether moieties. Oxidative cross-coupling of secondary benzylic ethers remains elusive. Herein, we describe the first cross-dehydrogenative coupling of secondary benzylic ethers with indoles and pyrroles for tertiary ether construction. A broad range of α-aryl substituted isochromans react with a variety of electronically varied indoles and pyrroles smoothly under mild metal-free conditions in high efficiency. In addition, the catalytic asymmetric variant was preliminarily explored, and corresponding tertiary ether was obtained in 69% ee.     

Hydrogen-mediated aldol reductive coupling of vinyl ketones catalyzed by rhodium: high syn-selectivity through the effect of tri-2-furylphosphine

[reaction: see text]. Catalytic hydrogenation of methyl vinyl ketone (MVK) and ethyl vinyl ketone (EVK) in the presence of diverse aldehydes at ambient temperature and pressure using tri-2-furylphosphine-ligated rhodium catalysts enables formation of aldol products with high levels of syn-diastereoselectivity. A progressive increase in diastereoselectivity is observed upon sequential replacement of phenyl residues for 2-furyl residues (Ph3P, FurPh2P, Fur2PhP, Fur3P). Hydrogen-labile functional groups, including alkynes, alkenes, benzylic ethers, and nitroarenes, remain intact under the coupling conditions.     

Copper(II) catalyzed cross-dehydrogenative coupling of cyclic benzylic ethers with simple carbonyl compounds by Na2S2O8

Copper(II) catalyzed cross-dehydrogenative coupling of cyclic benzylic ethers with a variety of simple carbonyl compounds mediated by Na₂S₂O₈ is developed. The scope of carbonyl components is broad, including simple aldehydes as well as ketones. The use of Na₂S₂O₈ as the oxidant for the CDC reaction is attractive based on economical and environmental factors.     

Copper Catalyzed Oxidative Esterification of Aldehydes with Alkylbenzenes via Cross Dehydrogenative Coupling

Copper(II) as the catalyst in a cross dehydrogenative coupling (CDC) reaction has been demonstrated for the synthesis of benzylic esters using aldehydes and alkylbenzenes as coupling partners.     

Iron-mediated cross dehydrogenative coupling (CDC) of terminal alkynes with benzylic ethers and alkanes

Iron-mediated sp-sp3 C-C bond formation through the cross dehydrogenative coupling(CDC) of terminal alkynes with benzylic ethers or alkanes has been developed.The inexpensive iron salt is used as the catalyst to make this transformation environmentally benign.Iron-mediated sp-sp3 C-C bond formation through the cross dehydrogenative coupling(CDC) of terminal alkynes with benzylic ethers or alkanes has been developed.The inexpensive iron salt is used as the catalyst to make this transformation environmentally benign.     

Samarium-promoted coupling of pyridine-based heteroaryl analogues of benzylic acetates with carbonyl compounds

2-Substituted pyridine, quinoline, isoquinoline, bipyridine, and 1,10-phenanthroline analogues of benzylic acetates undergo SmI(2)-promoted coupling with aldehydes and ketones to afford (2-hydroxyalkyl)heteroaromatics. [reaction: see text]     

Synthesis of indenyl ethers by gold(I)-catalyzed intramolecular carboalkoxylation of alkynes

The gold(I)-catalyzed carboalkoxylation of alkynes to form indanone derivatives from readily available ortho-acetylenic benzylic ethers is described. Importantly, the gold(I)-catalyzed rearrangement of enantioenriched benzylic ethers proceeds with chirality transfer, thus providing a practical method for the enantioselective synthesis of indenyl ethers.     

InCl3/Me3SiBr-catalyzed direct coupling between silyl ethers and enol acetates

A combined Lewis acid catalyst of InCl(3) and Me(3)SiBr promoted the direct use of enol acetates in the coupling with low-reactive silyl ethers, in which functional groups including ketones and aldehydes survived. Sterically hindered silyl ethers such as ROSiEt(3), ROSiPh(3), ROSit-BuMe(2), and ROSii-Pr(3) were also applicable.     

Direct oxidative C(sp3) -H cyanation of secondary benzylic ethers

A practical and efficient oxidative CH cyanation of secondary benzylic ethers with TMSCN in the presence of DDQ is described for the first time. The metal-free process is well tolerated with a wide variety of electronically varied α-monosubstituted isochromans for the synthesis of isochromans bearing α-aryl α-cyano substituent patterns.     

Straightforward three-component synthesis of diarylmethylpiperazines and 1,2-diarylethylpiperazines

Several functionalized diarylmethylpiperazines and 1,2-diarylethylpiperazines have been synthesized in moderate to high yield according to a one-step three-component coupling between an aromatic or a benzylic organozinc reagent, a piperazine derivative, and an aromatic aldehyde. The procedure can be extended to the synthesis of benzylpiperazine derivatives or β-arylethylpiperazines toward the use of paraformaldehyde or aliphatic aldehydes.     

Unexpected copper-catalyzed aerobic oxidative cleavage of C(sp3)-C(sp3) bond of glycol ethers

An unexpected Cu-catalyzed oxidative cleavage of the C(sp(3))-C(sp(3)) bond in glycol ethers by using air or molecular oxygen as the terminal stoichiometric oxidant is demonstrated. As a result, the corresponding α-acyloxy ethers and formates of 1,2-ethanediol are formed by direct coupling of carboxylic acids and aldehydes with glycol ethers under the reaction conditions. This method represents the first example of Cu-catalyzed aerobic cleavage of saturated C-C bond in ethers.     

A new route to spiro-ketals using the Horner-Wittig reaction of 2-diphenylphosphinoxy cyclic ethers

Two insect pheromones along with other spiro-ketals have been synthesised by a new route which involves Horner-Wittig coupling of 2-diphenylphosphinoxy cyclic ethers with aldehydes and lactols followed by acid catalysed cyclisation.     

Catalyse heterogene en presence de sels et sans solvant : II. Hydrosilylation d'aldehydes et de cetones satures et α,β ethyleniques

Hydrosilylation of saturated and α,β-unsaturated carbonyl compounds by heterogeneous catalysis without solvent and in the presence of salts (HCO2K, o-Ph(CO₂K)₂, FK, FCs) was carried out with good yields. FCs is a very efficient salt for hydrosilylation of aldehydes and ketones: for instance α-NpSiH₃ reacts quantitatively at room temperature with PhCOPh giving α-NpSi(OCHPh₂)₃. With α,β-unsaturated ketones FCs leads to 1,2-addition. It allows the isomerization of allysilyl ethers in silyl enol ethers, providing that the transferring hydrogen is benzylic.     

Indium-catalyzed coupling reaction between silyl enolates and alkyl chlorides or alkyl ethers

The coupling reactions of alkyl chlorides with silyl enolates catalyzed by InBr₃, and the coupling reactions of alkyl ethers with silyl enolates catalyzed by the combined Lewis acid of InBr₃/Me₃SiBr are described. In both reaction systems, various types of silyl enolates were used to give corresponding α-alkylated esters, ketones, carboxylic acids, amides, thioesters, and aldehydes.     

Samarium Triflate as Mild and Efficient Catalyst for Aza-Diels–Alder Reaction: A Facile Synthesis of cis-Fused Pyrano- and Furanoquinolines

Three-component coupling reactions of aldehydes, amines, and cyclic enol ethers have been carried out in the presence of samarium triflate to afford the corresponding pyrano and furanoquinolines in excellent yields with high endo-selectivity. The reaction conditions are mild and amenable to scale-up.     

Decarboxylative Benzylation of Aryl and Alkenyl Boronic Esters

The copper‐catalyzed decarboxylative benzylation of aryl and alkenyl boronic esters with electron‐deficient aryl acetates is reported. The oxidative coupling proceeds under mild, aerobic conditions and tolerates a host of potentially reactive electrophilic functional groups that would be problematic with traditional benzylation methods (aryl iodides and bromides, protic heteroatoms, aldehydes, Michael acceptors). A reaction pathway in which a benzylic nucleophile is generated by aryl acetate decarboxylation and in turn is intercepted by the catalyst to form diarylmethane products is supported by mechanistic studies.     

New mixed phosphonate esters by transesterification of pinacol phosphonates and their use in aldehyde and ketone coupling reactions with nonstabilized phosphonates

Alkylpinacol phosphonates were prepared by rhodium-catalyzed olefin hydrophosphorylation, and attempted alpha-deprotonation of the pinacol derived alkyl phosphonates resulted in ring cleavage. The propensity of the alkylpinacol phosphonates to undergo ring opening was exploited to prepare phosphonic acid monomethyl esters in high yield by transesterification in acidulated methanol. Esterification and alkylation with aldehydes or ketones gave beta-hydroxy mixed phosphonate esters. tert-Butyl and benzylic phosphonate ester protective groups were introduced to improve the efficiency and functional group compatibility of beta-hydroxy phosphonate saponification. The beta-hydroxy phosphonic acid monomethyl esters were dehydrated with diisopropylcarbodiimide, which gave oxaphosphetane intermediates that collapse to an olefin. The overall reaction sequence complements the arsenal of Horner-Wadsworth-Emmons-type coupling reactions.     

NH4Cl.CrO3对烯丙基醚和苄基醚的选择性氧化成酯的研究

本文报道了NH4Cl.CrO3(简称ACC)在无溶剂反应条件下, 以较好的产率, 将烯丙基醚或苄基醚选择性地氧化成相应的酯。     

Les organocadmiens benzyliques : obtention exclusive d'alcools: Secondaires d'addition avec l'acetaldehyde et le benzaldehyde

In contrast to the Grignard reaction, the reaction of various substituted benzylic cadmium reagents with aldehydes gives specifically secondary benzylic alcohols with good yields.     

Expedient Synthesis of Ketones via N‐Heterocyclic Carbene/Nickel‐Catalyzed Redox‐Economical Coupling of Alcohols and Alkynes†

An N‐heterocyclic carbene/nickel‐catalyzed direct coupling of alcohols and internal alkynes to form α‐branched ketones has been developed. This methodology provides a new approach to afford branched ketones, which are difficult to access through the hydroacylation of simple internal alkenes with aldehydes. This redox‐neutral and redox‐economical coupling is free from any oxidative or reductive additives as well as stoichiometric byproducts. These reactions convert both benzylic and aliphatic alcohols and alkynes, two basic feedstock chemicals, into various α‐branched ketones in a single chemical step.