Highly efficient and versatile chemoselective addition of amines to epoxides in water catalyzed by erbium(III) triflate

Er(OTf)₃ is proposed as a highly efficient and reusable catalyst for the opening of epoxides in water with aliphatic as well as aromatic amines leading to the synthesis of β-amino alcohols. The aqueous conditions employed in the present method will make it ‘environmentally friendly’ and potentially useful for industrial applications.     

Catalyst-free chemoselective N-tert-butyloxycarbonylation of amines in water

[Structure: see text] Catalyst-free N-tert-butyloxycarbonylation of amines in water is reported. The N-t-Boc derivatives were formed chemoselectively without any isocyanate, urea, N,N-di-t-Boc, and O/S-t-Boc as side products. Chiral amines, esters of alpha-amino acids, and beta-amino alcohol afforded optically pure N-t-Boc derivatives. Amino alcohol and 2-aminophenol afforded the N-t-Boc derivative without oxazolidinone formation. Selectivity was observed during competition of aromatic amine vs aliphatic amine, amine vs amino acid ester, amine vs amino alcohol, and primary amine vs secondary amine.     

Highly chemoselective reduction of azides to amines by Fe(0) nanoparticles in water at room temperature

A highly chemoselective reduction of aryl, heteroaryl, acyl and sulfonyl azides to the corresponding amines has been achieved by Fe(0) nanoparticles in water at room temperature in the absence of external hydride source. Several readily reducible functionalities including alkene, alkyne, S-S linkage, OTBDMS remain unaffected during reduction.     

Highly efficient ring opening reactions of epoxides with deactivated aromatic amines catalyzed by heteropoly acids in water

Heteropoly acid was found to be an effective and efficient catalyst for the ring opening reaction of epoxides with various aromatic amines to produce the corresponding β-amino alcohols in moderate to excellent yields in water. This method provides a new and efficient protocol in terms of mild reaction conditions, clean reaction profiles, small quantity of catalyst, and simple work-up procedure.     

Highly stereoselective synthesis of homoallylic amines based on addition of allyltrichlorosilanes to benzoylhydrazones

Allyltrichlorosilanes reacted with benzoylhydrazones in DMF without the use of any catalyst to afford the corresponding homoallylic benzoylhydrazines in good to high yields. The reactions proceeded at 0 degrees C to room temperature under mild conditions. In addition, it was found that the reactions tolerated well the steric hindrance of hydrazones and allyltrichlorosilanes. Indeed, ketone-derived benzoylhydrazones reacted with allyltrichlorosilane smoothly to afford the corresponding N'-tert-alkyl-N-benzoylhydrazines in high yields. In crotylation with (E)- and (Z)-crotyltrichlorosilanes, syn- and anti-adducts were stereospecifically obtained, respectively. These reactions are most likely to proceed via a cyclic chairlike transition state where the R group takes an axial position. When alpha-heteroatom-substituted chiral benzoylhydrazones were used, high anti-diastereoselectivities were observed. These adducts can be readily converted to homoallylic amines in high yields without epimerization.     

Highly efficient procedure for the conjugate addition of amines to electron deficient alkenes

The novel efficient procedure has been developed for the conjugate addition of amines to electron deficient alkenes. The results showed that the catalyst was very efficient for the reactions with the excellent yields in several minutes. Operational simplicity, without need of any solvent, low cost of the catalyst used, high yields, reusability, excellent chemoselectivity, applicability to large-scale reactions are the key features of this methodology. The article is published in the original.     

Highly diastereoselective radical addition to glyoxylate imines of chiral amines without additional heteroatoms

The diastereoselective addition of alkyl radicals to glyoxylate imines of α-alkylbenzylamines has been investigated and it was found that diastereoselectivity improved as the size of the alkyl group increased.     

Recent advances in chemoselective acylation of amines

N-chemoselective acylation of amines in the presence of competing nucleophiles, like alcohols and thiols, is by no means a simple achievement in organic synthesis and even more difficulties arise when distinctions between primary, secondary, and aromatic amines need to be made. The present digest will review some recent achievements in this field, ranging from transamidation reactions to carboxylic acid derivatives transacylations. In addition, more creative strategies, involving chemoenzymatic reactions and metal-catalyzed acylations and carbonylations, will be discussed in order to furnish a concise view of the state-of-the-art approaches to this synthetic challenge.     

β-Cyclodextrin promoted aza-Michael addition of amines to conjugated alkenes in water

Highly efficient and environmentally benign aza-Michael additions of amines to α,β-unsaturated compounds catalyzed by β-cyclodextrin in water to produce the corresponding β-amino compounds in excellent yields under mild conditions are described. β-Cyclodextrin can be recovered and reused in subsequent reactions without loss of activity.     

Regioselective ring opening in epoxides under the action of amines in water medium

Amino(bis-amino)derivatives of 2-propanol were synthesized by ring opening in epoxides under the action of amines in water medium using environmentally safe methods. The structure of the compounds obtained was established by elemental analysis and the IR, ¹H and ¹³C NMR spectroscopy. It was found that these substances are effective bactericides. They suppress the growth of the sulfate-reducing bacteria and exhibit high anticorrosive properties.     

Highly efficient heterogeneous procedure for the conjugate addition of amines to electron deficient alkenes

The novel efficient procedure has been developed for the conjugate addition of amines to electron deficient alkenes. K₂CO₃ supported on different carriers have been synthesized for the conjugate addition of amines and alkenes. After optimizing the reaction conditions, K₂CO₃/MgO was chosen as the most efficient catalyst for the reactions. The results showed that the catalyst was very efficient for the conjugate addition of amines to electron deficient alkenes with the excellent yields in several minutes. Operational simplicity, without need of any solvent, low cost of the catalyst used, high yields, reusability, excellent chemoselectivity, and applicability to large-scale reactions are the key features of this methodology. Supported by the National Key Project of Scientific and Technical Supporting Programs Funded by Ministry of Science and Technology of China (Grant No. 2006BAE03B06), Shanghai Leading Academic Discipline Project (Grant No. B409), and Shanghai International Cooperation of Science and Technology Project (Grant No. 06SR07101)     

Highly chemoselective hydrogenolysis of iodoarenes

The catalytic hydrodehalogenation reaction using molecular hydrogen and Pd/C has been revisited. It is shown that the speed of removal of halogen increases with increasing electronegativity I < Br < Cl. Nevertheless, selective dehydrohalogenation in compounds containing other reducible functions can be achieved only with iodine and not with bromine or chlorine. Selective deiodination of iodobenzophenone could be accomplished without reducing the carbonyl group. Hydrogenolysis of azidoiodoaromatic compounds to the corresponding azido compounds is high yielding. This selectivity was exploited for the labeling of benzophenone- and azido-containing compounds by deuterium and tritium.     

Zinc-catalyzed chemoselective reduction of tertiary and secondary amides to amines

General and convenient procedures for the catalytic hydrosilylation of secondary and tertiary amides under mild conditions have been developed. In the presence of inexpensive zinc catalysts, tertiary amides are easily reduced by applying monosilanes. Key to success for the reduction of the secondary amides is the use of zinc triflate and disilanes with dual Si-H moieties. The presented hydrosilylations proceed with excellent chemoselectivity in the presence of sensitive ester, nitro, azo, nitrile, olefins, and other functional groups, thus making the method attractive for organic synthesis.     

Green protocol for conjugate addition of amines to p-quinones accelerated by water

Amines undergo smooth conjugate addition to p-quinones in H₂O at ambient temperature in the absence of a catalyst to produce 2-aminoquinones in excellent yields. Significant rate acceleration of this reaction is observed in H₂O compared to organic solvents. H₂O played a dual role in simultaneously activating the p-quinone and amine. This new methodology constitutes an easy, highly efficient, and green synthesis of substituted p-quinones. Correspondence: J. S. Yadav, Division of Organic Chemistry, Indian Institute of Chemical Technology, Hyderabad 500007, India.     

Highly chemoselective calcium-catalyzed propargylic deoxygenation

A calcium-catalyzed direct reduction of propargylic alcohols and ethers has been accomplished by using triethylsilane as a nucleophilic hydride source. At room temperature a variety of secondary propargylic alcohols was deoxygenated to the corresponding hydrocarbons in excellent yields. Furthermore, for the first time, a catalytic deoxygenation of tertiary propargylic alcohols was generally applicable. The same protocol was suitable for an efficient reduction of secondary as well as tertiary propargylic methyl, benzyl and allyl ethers. Substrates containing an additional keto-, ester or secondary hydroxyl function were reduced with exceptional chemoselectivity at the propargylic position.     

Catalyst-free regioselective ring opening of epoxides with aromatic amines in water and solvent-free conditions

Without using any catalysts, a variety of epoxides undergo ring-opening by aromatic amines to afford the corresponding 1,2-amino alcohols in high to excellent yields with good regioselectivity in the presence of water as solvent and under solvent-free conditions.     

Highly chemoselective reductive amination by one pot reaction of aldehydes, amines and Dihydropyridine Catalyzed by TMSCl

More efficient, cost effective and metal free DHP/TMSCl system for one pot reductive amination of aldehydes was developed. The method allows the efficient one pot synthesis of structurally diverse amines with Hantzsch ester as the hydrogen source in the presence of trimethylsilyl chloride as a catalyst in high to quantitative yields under mild conditions.     

Highly chemoselective and stereocontrolled access to 6-alpha-allyl penicillanates

Treatment of 6-bromo penicillanates with allyltributyltin under free-radical conditions results in the formation of 6-alpha allyl derivatives.     

Conjugate addition of aromatic amines to ethenetricarboxylates

The conjugate addition of amines is considered to be a useful reaction in synthetic organic chemistry. The reaction of reactive electrophilic olefins, ethenetricarboxylates, and aromatic amines with and without catalytic Lewis acids such as ZnCl₂ and ZnBr₂ at room temperature gave amine adducts in high yields. The products were converted to α-amino acid, dl-aspartic acid derivatives. Using Lewis acids such as Sc(OTf)₃ and Zn(OTf)₂ at higher temperature (40-80 °C), the reaction of ethenetricarboxylates and N-methylaniline gave an aromatic substitution product. A catalytic enantioselective conjugate addition using a chiral Lewis acid was also investigated. For example, the reaction of 1,1-diethyl 2-tert-butyl ethenetricarboxylate with N-methylaniline in the presence of chiral bisoxazoline-Cu(II) complex in THF at −20 °C for 17 h gave an amine adduct in 91% yield and 78% ee. On the other hand, the reaction with aniline and primary aniline derivatives gave adducts with almost no ee%.