Chemoselective reductive alkylation of ammonia with carbonyl compounds: synthesis of primary and symmetrical secondary amines

An efficient, general procedure for highly chemoselective reductive mono-alkylation of ammonia with ketones is reported. Treatment of ketones with ammonia in ethanol and titanium(IV) isopropoxide, followed by in situ sodium borohydride reduction, and a straightforward workup afforded primary amines in good to excellent yields. Reductive alkylation of ammonia with aldehydes, on the other hand, afforded the corresponding symmetrical secondary amines selectively.     

Double nucleophilic reaction of amines to the imidazole nucleus and selective synthesis of 5-aminoimidazoles

Reaction of 2-(1-chloro-2,2-dimethylpropyl)-1-methyl-1H-imidazole with an excess of N,N-dimethylamine at room temperature gave an abnormal adduct, trans-4,5-bis(dimethylamino)-1-methyl-2,2-dimethylpropyl-2-imidazoline, which was derived from a serial, double nucleophilic addition into the imidazole nucleus in 74% yield together with a normal S_N product, 1-methyl-2-(1-dimethylamino-2,2-dimethylpropyl)-1H-imidazole in 15% yield. The former was easily converted to 1-methyl-5-(dimethylamino)-2-(2,2-dimethylpropyl)-1H-imidazole by only reflux in toluene in 90% yield. The scope, mechanism and limitation of these reactions are discussed.     

二茂镁的原位合成及其与羰基化合物的反应

研究了通过萘锂还原法制得的活性镁与环戊二烯原位合成环戊二烯基镁(Cp~2Mg)的方法。Cp~2Mg的存在是由它与醛酮反应生成富烯得到证实。此法产率高, 方法简单, 条件温和。     

镝促进下醛、酮与炔丙基溴及苯基炔丙基溴的高 选择性反应

在金属镝的促进下,醛、酮可与炔丙基溴反应,高选择性高产率地得到相应的高炔丙醇,没有发现连二烯醇的存在。当用苯基炔丙基溴代替炔丙基溴与醛、酮反应时,主要得到了相应的连二烯醇,而没有发现高炔丙醇的存在,由此提出了六元环过渡态的反应机理。     

Regioselective synthesis of linalyl compounds via addition reaction of geranyl bromide and tin with carbonyl compounds

Linalyl alkyl or aryl carbinols were regioselectively synthesized by the reaction ofgeranyl bromide and powdered tin with aldehydes and ketones.     

The reaction between methylene dialuminum tetrabromide and carbonyl compounds,synthesis of olefins

The reaction between carbonyl compounds and methylenedialuminum tetrabromide or methylenelithium aluminum dibromide in dry THF gives the corressponding methylenic olefins in satisfactory yields.     

Oxidative amide synthesis directly from alcohols with amines

Transition metal catalyzed oxidative amide synthesis directly from primary alcohols and amines is a highly atom economical transformation that evolves hydrogen gas as the only by-product. Several Ru-, Rh-based homogeneous and Ag-based heterogeneous catalysts have been developed for direct amide synthesis. Most of the developed catalysts showed excellent activity with sterically unhindered alcohols and amines; however, limited activity was observed with sterically hindered alcohols or amines, less basic aryl amines, and secondary amines. This account provides an overview of recent advances and challenges in direct amide synthesis.     

General and selective synthesis of primary amines using Ni-based homogeneous catalysts

The development of base metal catalysts for industrially relevant amination and hydrogenation reactions by applying abundant and atom economical reagents continues to be important for the cost-effective and sustainable synthesis of amines which represent highly essential chemicals. In particular, the synthesis of primary amines is of central importance because these compounds serve as key precursors and central intermediates to produce value-added fine and bulk chemicals as well as pharmaceuticals, agrochemicals and materials. Here we report a Ni-triphos complex as the first Ni-based homogeneous catalyst for both reductive amination of carbonyl compounds with ammonia and hydrogenation of nitroarenes to prepare all kinds of primary amines. Remarkably, this Ni-complex enabled the synthesis of functionalized and structurally diverse benzylic, heterocyclic and aliphatic linear and branched primary amines as well as aromatic primary amines starting from inexpensive and easily accessible carbonyl compounds (aldehydes and ketones) and nitroarenes using ammonia and molecular hydrogen. This Ni-catalyzed reductive amination methodology has been applied for the amination of more complex pharmaceuticals and steroid derivatives. Detailed DFT computations have been performed for the Ni-triphos based reductive amination reaction, and they revealed that the overall reaction has an inner-sphere mechanism with H₂ metathesis as the rate-determining step.

A Ni-triphos based homogeneous catalyst enabled the synthesis of all kinds of primary amines by reductive amination of carbonyl compounds with ammonia and hydrogenation of nitroarenes.     

The reaction of selenophosphonates with carbonyl compounds. Vinylic selenides

Selenophosphonates of the general formula (EtO)₂P(O)CHRSePh were prepared and their reactions with aldehydes and ketones investigated. The products formed are vinylic selenides having predominantly the E configuration. Hydrolytic cleavage of these products gives the corresponding ketones.     

Highly selective synthesis of tricyclic compounds from semithioglycoluril,formaldehyde and amines

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The oxidation of the alpha-carbon of amines in hydrothermal condition: an alternative synthetic route of compounds containing amide bond

Here we report experimental evidence for the simple synthesis of N,N-diethylhydroxylamine and an amide bond formation reaction from oxidation of the alpha-carbon of tertiary amines by the reaction of triethylamine and hydrogen peroxide in hydrothermal conditions. It is proved that 120 °C is a turning point: when the temperature is lower than that, the main product is N,N-diethylhydroxylamine as a result of a cope rearrangement reaction mechanism; on the contrary, the product is more complex and the main products are amides via a radical chain mechanism involving three steps: initiation, propagation, and oxidation, followed by decarbonylation and electrocyclization because the radical is easier to form under high temperature.     

Iron-mediated electrochemical reaction of alpha-chloroesters with carbonyl compounds

[reaction: see text] Reformatsky-type reactions have been performed efficiently using an electroassisted iron-complex catalysis. Valuable product such as beta-hydroxyesters, ketones or nitriles are thus prepared with high yields.     

Simple synthesis of alpha-hydroxyamino carbonyl compounds: new scope of the nitroso aldol reaction

[reaction: see text] The reaction of nitroso compounds with enolates, "the nitroso aldol reaction", occurs in high yield to generate alpha-hydroxyamino carbonyl compounds. Yields range from 42% to 98% with N-selectivity >99:1 from commercially available aromatic or aliphatic nitroso compounds and a variety of alkali metal or tin enolates.     

Three-component synthesis of spiro compounds with a carbamate functionality

1,3-Dipolar cycloaddition of methyl 4-[2-(2-oxo-1,2-dihydro-3H-indol-3-ylidene)acetyl]phenylcarbamate to non-stabilized azomethine ylides generated by decarboxylation of α-amino acid (sarcosine and proline) adducts with ketones (isatin and ninhydrin) occurred regioselectively with formation of the corresponding spiro compounds having a carbamate moiety.     

A new tandem reaction of benzyne: one-pot synthesis of aryl amines containing anthracene

[reaction: see text] The reaction of benzyne with N-substituted imidazoles affords a novel way to prepare arylamines containing anthracene under very mild conditions. This transformation is assumed to proceed via a tandem reaction involving a Diels-Alder reaction and an intermolecular nucleophilic coupling reaction.     

Rhenium-catalyzed reaction of carbonyl compounds with ketene silyl acetals

It was found that rhenium complex is an effective catalyst for the reaction of carbonyl compounds with ketene silyl acetals. A wide range of β-silyloxy esters is obtained by the treatment of carbonyl compounds with ketene silyl acetals in the presence of a catalytic amount of ReBr(CO)₅ in moderate to good yields.