Palladium-catalyzed asymmetric allylic alkylation of electron-deficient pyrroles with meso electrophiles

Pyrroles can serve as competent nucleophiles with meso electrophiles in the Pd-catalyzed asymmetric allylic alkylation. The products from this transformation were obtained as a single regio- and diastereomer in high yield and enantiopurity. A nitropyrrole-containing nucleoside analogue was synthesized in seven steps to demonstrate the synthetic utility of this transformation.     

New reactions of 2,3-diaminonaphthaline with carbonyl electrophiles

The reaction of 2,3-diaminonaphthalene with dimedone gave 3-[(3-amino-2-naphthyl)amino]-5,5-dimethylcyclohex-2-en-1-one that reacts with alloxan to afford a product of addition at the enamine moiety. The latter is converted to a spiro derivative on heating in CF₃COOH, or undergoes condensation with 2,6-di-tert-butyl-p-benzoquinone to give a benzophenazinone derivative with a sterically hindered phenol substituent.     

Fluoride ion induced reactions of organosilanes with electrophiles

Benzyl- 4-picolyl- and phenylallyl(trimethyl)silanes react with electrophiles in the presence of KF/18-crown-6 or silica-TBAF under mild conditions.     

Cleavage reactions of the aziridine ring

N-Arylethylenimines react with ethylene oxide in the presence of tetraethylammonium bromide with the formation of N-arylmorpholines. In a number of cases, N,N'-diarylpiperazines were isolated as by-products. Ethylene sulfide does not react with N-arylethylenimines.For part II, see [1].     

Fission reactions of the aziridine ring

Reaction of N-arylethylenimines with carbon dioxide in the presence of tetraethylammonium bromide gives N-aryl-2-oxazolidones, with N,N-diarylpiperazines as by-products. Carbon disulfide reacts with N-arylethylenimines under similar conditions to give 11 copolymers, together with small amounts of N-arylthiazolidine-2-thiones. Carbon oxysulfide gives copolymers only. The copolymers are converted at 250° C into N-arylthiazolidine-2-thiones and N-arylthiazolidones, respectively. N-Arylethylenimines react with phenyl isothiocyanates to give 2-phenylimino-3-arylthiazolidines.For part III, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, Vol. 6, No. 5, pp. 611–615, May, 1970.     

Selective alkylation reactions with vinamidinium salts

Vinamidinium salts react readily with enolates of ketones, esters, and lactones to produce multifunctional, synthetically-useful, dienaminones.     

Phase-Transfer catalyzed alkylation of morpholine with 1,2-dichloroethane

Russian Journal of General Chemistry -     

Phase-transfer catalyzed asymmetric arylacetate alkylation

Phenethyl arylacetates are alkylated under phase-transfer conditions with cinchona catalysts with alkyl halides in high yield with excellent enantioselectivity (84-99% ee) following recrystallization. Cinchonidine (CD) derived catalyst gave the (R)-product and cinchonine (CN) catalyst produced the (S)-product. The phenethyl (PE) ester group is removed, using ammonium formate and catalytic Pd/C, to give alkylated carboxylic acid products in high selectivity. The utility of the approach is demonstrated by a direct synthesis of (S)-naproxen^™.     

Stereoselective reactions of a thioester butanediacetal with various electrophiles

The reactions of the lithium enolate of S-ethyl (2R,5R,6R)-5,6-dimethoxy-5,6-dimethyl-[1,4]-dioxane-2-carbothioate were investigated in the presence or absence of hexamethylphosphoramide (HMPA). Fluorination gave a single isomer with a much better yield than for the corresponding methyl ester. Alkylation with alkyl halides strongly depended upon their structure. Without HMPA, only methyl iodide reacted with moderate yield and gave a single isomer. In the presence of HMPA, all of the alkyl halides reacted almost quantitatively (81–98% yield) with moderate stereoselectivity and preferentially gave products with the alkyl chain attached at the equatorial position. The silyl enol ether obtained from the thioester had the opposite geometry to that obtained from the methyl ester, which thus explains the difference in stereoselectivity between these two compounds.     

Nickel catalyzed cross-coupling of aryl C-O based electrophiles with aryl neopentylglycolboronates

The efficiency of mesylates, sulfamates, esters, carbonates, carbamates, and methyl ethers as C-O-based electrophiles attached to the 1- or 2-position of naphthalene and to activated and nonactivated phenyl substrates was compared for the first time in Ni-catalyzed cross-coupling with phenyl neopentylglycolboronates containing electron-rich and electron-deficient substituents in their para-position. These experiments were performed in the presence of four different Ni(II)- and Ni(0)-based catalysts. Ni(II)-based catalysts mediate the cross-coupling of most 2-naphthyl C-O electrophiles with both arylboronic acids and with neopentylglycolboronates when K(3)PO(4) is used as base. The same catalysts are not efficient when CsF is used as base. However, Ni(0)-based catalysts exhibit selective efficiency, and when reactive, their efficiency is higher than that of Ni(II)-based catalysts in the presence of both K(3)PO(4) and CsF. These results provide both reaction conditions for the cross-coupling, and for the elaboration of orthogonal cross-coupling methodologies of various C-O based electrophiles with aryl neopentylglycolboronates. With the exception of mesylates and sulfamates the efficiency of all other 2-naphthyl C-O electrophiles was lower in cross-coupling with aryl neopentylglycolboronates than with arylboronic acids.     

1-(Phenylethynyl)aziridine in reactions with amines

The reaction of 1-(phenylethynyl)aziridine with a primary or secondary amine gave 2-benzylimidazoline-2 or N-aminoethyl substituted phenylacetamidine via nucleophilic attack on the aziridine ring. The mechanism of aziridine ring opening by an amine was studied.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 600–603, May, 1989.     

Lewis base catalyzed Mannich-type reactions between trimethylsilyl enol ethers and aldimines

Lewis base catalyzed Mannich-type reaction between trimethylsilyl enol ethers and N-tosylaldimines is described. Nitrogen anions generated from amides or imides such as lithium benzamide or potassium phthalimide are found to be effective Lewis base catalysts in DMF at room temperature to afford the corresponding beta-amino carbonyl compounds in good to high yields; the oxygen anion generated from carboxylic acids such as lithium acetate was also found to be effective in dry DMF. The above-mentioned lithium acetate-catalyzed Mannich-type reaction between aldimines and various trimethylsilyl (TMS) enol ethers such as silyl ketene acetal proceeded smoothly even in water-containing DMF. Then, Lewis base catalyzed three-component Mannich-type reactions of TMS enol ether, tosylamide, and aromatic aldehyde having electron-withdrawing group such as p-nitrobenzaldehyde were investigated. The reaction proceeded smoothly to afford the corresponding beta-amino ester in good yield. Further, ammonium carboxylates such as tetrabutyl ammonium acetate or tetrabutyl ammonium benzoate were found to be more effective Lewis base catalysts in the above-mentioned Mannich-type reaction. The synthesis proceeded in various solvents at lower temperatures. The reaction between aldimines and TMS enol ethers generated from thioester and various ketones such as propiophenone or cyclohexanone also proceeded smoothly to afford the corresponding beta-amino carbonyl compounds in high yields with good to high anti-selectivities.     

Olefin isomerization reactions catalyzed by ruthenium hydrides bearing Schiff base ligands

A series of in situ‐generated ruthenium hydride complexes Ru(PPh₃)₂(CO)H(Lⁿ) (n = a – h ) incorporating a Schiff base ligand was investigated for the isomerization of olefins. ¹H‐NMR was used to characterize the new hydride species in combination with ³¹P‐NMR. Allylbenzene and 1‐octene were used as model substrates. Temperature, solvents and catalyst/substrate mole ratio were taken into account as parameters to optimize the isomerization reaction. All catalysts showed the best performance in 2‐butanol, suggesting that the catalytic activity depends not only strongly on the steric and electronic environment of the ruthenium but also on the chosen solvent. Copyright © 2011 John Wiley & Sons, Ltd.     

Nickel catalyzed decarboxylative alkylation of aryl triflates with anhydrides

Aliphatic acid anhydrides are the versatile building blocks and the new method for the conversion of anhydrides is thus of great significance. Herein, we report the decarboxylative alkylation of aryl triflates with aliphatic acid anhydrides via nickel catalysis. This novel method provides a facile access to construct Csp²-Csp³ bond. In addition, this method is compatible with a broad array of functional groups and exhibits good substrates scope.     

Efficient alkylation of ketones with primary alcohols catalyzed by ruthenium(II)/P,N ligand complexes

An efficient catalytic system containing [RuCl₂(η⁶-p-cymene)]₂ and one P,N ligand, N-diphenylphosphino-2-aminopyridine (L1) was loaded in catalyzing the alkylation of ketones with primary alcohols for a diverse array of substrates. Other five P,N ligands based on pyridin-2-amine and pyrimidin-2-amine were also examined in this reaction to explore the influence of steric hindrance and electronic effects. Monitoring by ¹H NMR and ESI-MS reveals a stable cationic L1-coordinated ruthenium hydride intermediate, identified as [Ru(η⁶-p-cymene)(κ²-L1)H]⁺. Organic intermediates consistent with a three-step dehydrogenation, alkylation and hydrogenation pathway were also observed. The final step in this reaction, the ruthenium-catalysed transfer hydrogenation reduction of α,β-unsaturated ketone with benzyl alcohol was performed separately.     

Highly efficient allyl cross-coupling reactions of allylindiums with organic electrophiles

This paper describes highly efficient allyl cross-coupling reactions of allylindiums with organic electrophiles such as aryl and vinyl triflates, vinyl halides, dibromoolefin, and alkynyl iodide. The reactions were carried out using 4 mol % Pd(PPh3)4 in the presence of 3 equiv of LiCl in DMF at 100 degrees C under a nitrogen atmosphere. Allylindium, generated from the reaction of 1 equiv of indium with 1.5 equiv of allyl halide, gave the best result as a coupling partner. The present method is mild and simple to apply, and it produces a diverse range of allylic compounds in good to excellent yields.     

Guanidines based on tryptamine and histamine in reactions with electrophiles

Reactions of 4,6-dimethylpyrimidin-2-ylcyanamide with tryptamines and histamine gave the corresponding disubstituted guanidines. The molecular parameters of the products were calculated using GAUSSIAN 03 software package. The direction of electrophilic attack on these compounds was predicted on the basis of the geometric shape of their highest occupied molecular orbital (HOMO) and molecular electrostatic potential (MEP) maps. Acyl, carbamoyl, and cyclic derivatives were obtained, whose structure was consistent with the results of quantum-chemical calculations.     

Phenol alkylation with tert-butyl alcohol catalyzed by HM zeolite

Zeolite HM has a potential application in phenol alkylation with tert-butyl alcohol to produce p-TBP and 2,4-DTBP with high activity and selectivity.     

Organic azo complexes of molybdenum and their reactions with electrophiles

Organic azo(1) and N,N-disubstituted hydrazido-N'(2) complexes of molybdenum have been prepared by the reactions of certain molybdenum-oxo complexes with hydrazines.