Reactions of N,N-dimethylamino(diphenylphosphoryl)chloromethane with alkan-2-ones

The direction of the reaction of N,N-dimethylamino(diphenylphosphoryl)chloromethane with alkan-2-ones depends on the ketone structure. N,N-Dimethylamino(diphenylphosphoryl)-chloromethane reacts with linear alkan-2-ones following the Abramov-type reaction to give α-phosphorylated alcohols, while the reaction with branched alkan-2-ones and acetophenone proceeds as the Mannich-type reaction affording the phosphorylated Mannich bases.     

Kinetic parameters of radical reactions of 2-mercaptobenzothiazole with quinone imines

The chain reaction of N,N′-diphenyl-1,4-benzoquinone diimine with 2-mercaptobenzothiazole was studied by two methods developed earlier for the nonchain reaction of N-phenyl-1,4-benzoquinone monoimine with 2-mercaptobenzothiazole. In the methods used, the kinetic scheme of the reaction is simplified by creating conditions under which the rates of all stages except radical generation and decay can be neglected. One of the methods was updated. For the nonchain reaction of N-phenyl-1,4-benzoquinone monoimine with 2-mercaptobenzothiazole, both methods gave close results; for the chain reaction of N,N′-diphenyl-1,4-phenylenediamine with 2-mercaptobenzothiazole, the results differed by approximately one order of magnitude.     

Chiral base-catalyzed aldol reaction of trimethoxysilyl enol ethers: effect of water as an additive on stereoselectivities

An aldol reaction of trimethoxysilyl enol ether catalyzed by lithium binaphtholate is described. The aldol reaction of trimethoxysilyl enol ether derived from cyclohexanone under anhydrous conditions predominantly afforded the anti-aldol adduct with moderate enantioselectivity, whereas the reaction under aqueous conditions predominantly resulted in the syn-adduct and the enantioselectivity of the syn-adduct was considerably improved. The best enantioselectivity was obtained in the reaction of trimethoxysilyl enol ether derived from 1-indanone with cyclohexanecarboxaldehyde (97% ee (syn)). This is the first example of an aldol reaction of trimethoxysilyl enol ether catalyzed by a chiral base.     

Substituent-controlled domino-Knoevenagel-hetero Diels-Alder reaction—a one-pot synthesis of polycyclic heterocycles

The reaction of 2-(N-alkenyl-N-aryl)amino-4-oxo-4H-1-benzopyran-3-carbaldehyde with dimedone/Meldrum’s acid/4-hydroxycoumarin by heating in ethanol in the presence of pyridine produces polycyclic heterocycles bearing pyridine and pyran rings in a one-pot reaction. The effect of substituents on N-atom of the amino function controls the mode of reaction. Terminal alkenes prefer intramolecular Michael type reaction, but non-terminal alkenes favour Diels-Alder reaction, whereas, under similar condition, 2-(N-alkyl-N-allyl)amino-4-oxo-4H-1-benzopyran-3-carbaldehyde undergoes domino-Knoevenagel-hetero Diels-Alder reaction.     

Synthesis of fluorinated imines and carbodiimides from azides via aza-Wittig reaction

The Staudinger reaction of fluoroalkylazides were studied. A series of N-fluoroalkylimines were synthesized via aza-Wittig reaction of N-fluoroalkyliminophosphoranes. The N,N′-difluoroalkylated carbodiimide was also synthesized via the reaction of N-fluoroalkyliminophosphoranes with carbon dioxide or carbon disulfide.     

Temperature vs. time sequences to palliate deactivation in parallel and in series-parallel with the main reaction: parametric study

The calculation of temperature vs. time sequences to palliate catalyst deactivation in an integral reactor has been studied either by maintaining constant the conversion at the reactor outlet in a simple reaction or by maintaining constant the concentration of a given component at the outlet in a complex reaction system. The experimental systems studied, which are a simple one (dehydration of 2-ethylhexanol) and a complex one (isomerization of cis-butene), have kinetic models of the Langmuir-Hinshelwood-Hougen-Watson type for the main reaction and deactivation, with deactivation by coke dependent on the concentration of the reaction components. In the reaction of dehydration of 2-ethylhexanol deactivation occurs in parallel with the main reaction and in the isomerization of cis-butene deactivation occurs in series-parallel with the main reaction. A parametric study has been carried out for both reaction systems. The sequences calculated have been experimentally proven in an automated reaction apparatus.     

Verbanone in the synthesis of amidoketones from o-menthane series

A verbanone reaction with acetonitrile under Ritter reaction conditions led to a selective formation of o-menthane derivatives, a mixture of stereoisomeric cis-and trans-8-acetamido-o-menthones. The streoisomers ratio depends on the reaction conditions and the character of acid catalyst used.     

Synthetic transformations of isoquinoline alkaloids. 1-alkynyl-3,6-dimethoxy-N-methyl-4,5α-epoxy-6,18-endoethenobenzo[i]isomorphinans and their transformations

The reaction of thebaine with 2-bromo-6-methyl-1,4-benzoquinone regioselectively afforded 6,18-endo-etheno-9-methyldihydrothebainehydroquinone. Iodination of 6,18-endo-ethenodihydrothebainehydroquinones with N-iodosuccinimide in trifluoroacetic acid was also selective, and the corresponding 1-iodo derivatives were formed. The main reaction pathway in the halogenation of 6,18-endo-ethenodihydrothebainehydroquinone with iodine chloride was chlorination of the fused hydroquinone fragment. The Sonogashira reaction of 1-iodo-6,18-endo-ethenodihydrothebainehydroquinones with trimethylsilylacetylene and subsequent desilylation gave 1-ethynyl-6,18-endo-ethenodihydrothebainehydroquinones. 1-[3-(4-R-Piperazin-1-yl)-propynyl]- and 1-{3-[2-(pyridin-3-yl)piperidin-1-yl]propynyl}-6,18-endo-ethenodihydrothebainehydroquinones were synthesized by the Mannich reaction of acetylenic derivatives of dihydrothebainehydroquinone with piperazine and anabasine in the presence of formaldehyde, catalyzed by copper(I) compounds. The reaction of 1-iodo-6,18-endo-ethenodihydrothebainehydroquinone with N-methylpiperazine and formaldehyde was accompanied by copper-catalyzed oxidative homocoupling.     

Experimental and DFT study of the aza-Diels-Alder reaction between cyclopentadiene and protonated benzylimine derivated from glyoxylates

The Diels-Alder reaction of protonated N-benzyl imine of methyl glyoxylate with cyclopentadiene in different solvents gave mixtures of exo/endo adducts. The exo/endo selectivity of the reaction was elucidated by NMR experiments. Theoretical calculations by means of density functional theory (DFT) at the B3LYP/6-31G(d) level have also been performed to elucidate the molecular mechanism of this reaction. The DFT results suggest a highly asynchronous concerted mechanism, which in turn can explain the preferred exo stereoselectivity of the reaction. Inclusion of solvent effects enhances the exo selectivity, and this effect increases with the polarity of the solvent, in good agreement with the experimental findings.     

Synthesis of cis bis-β-lactams via Staudinger cycloaddition reaction using C2-symmetric 1,2-diamines

An efficient stereoselective synthesis of bis-β-lactams via cycloaddition reaction (Staudinger reaction) of ketenes with bisimines derived from C₂-symmetric 1, 2-diamines is described. The reaction provided diastereomeric mixture of meso and C₂-symmetric cis-bis-β-lactams with higher selectivity for meso-bis-β-lactams.     

N-Tosylaziridine, a new substrate for chemical fixation of carbon dioxide via ring expansion reaction under atmospheric pressure

N-Tosylaziridine was found to be a useful substrate for cycloaddition reaction with carbon dioxide. The reaction was successfully catalyzed by lithium bromide under atmospheric pressure to give the corresponding five-membered cyclic urethane, N-tosyl-1,3-oxazolidin-2-one, selectively. It was found that electron-donating nature of the substituent at 2-position of N-tosylaziridine accelerated the reaction, and this tendency allowed us to estimate the reaction mechanism.     

Synthesis of unsymmetrical biaryl ureas from N-carbamoylimidazoles: kinetics and application

N-Carbamoylimidazoles dissociate in solution to yield imidazole and an isocyanate that may be reacted with another aryl amine to form an unsymmetrical biaryl urea. This paper investigates the reaction kinetics and the influence of electron withdrawing/donating substituents on the reaction of N-carbamoylimidazoles with aniline. The overall reaction mechanism involves two zwitterionic intermediates, formed during dissociation and upon reaction of the liberated isocyanate with aniline. The rate limiting step for the reaction is a base catalysed proton transfer from the second zwitterionic intermediate. Although electron withdrawing substituents on the aryl group hinder dissociation, they significantly increase reaction rates compared to compounds bearing electron donating substituents. The imidazole liberated upon dissociation catalyses the rate determining step so that reactions of dissociated N-carbamoylimidazoles proceed more rapidly than those involving only isocyanates. In addition, the imidazole eliminates the need for anhydrous reaction conditions. The N-carbamoylimidazole methodology was demonstrated by preparing sorafenib, a biaryl urea kinase inhibitor, in good yield and excellent purity.     

Hydrochalcogenation of activated olefines. Synthesis of functionalized dialkylchalcogenides

Alkanethiols, selenols and tellurols are generated in situ by reaction of elemental sulfur, selenium and tellurium with commercial alkyllithiums, followed by reaction with deoxygenated water. The alkanechalcogenols react in situ with activated olefins in a Michael-type addition reaction.     

Reaction des lithiens avec les organophosphores. Reaction d'addition du t-butyllithium sur le noyau benzenique des sels de phenylphosphoniums

A new reaction of organolithium compounds with phosphonium salts is described; reaction of t-butyllithium with dibenzylaminophosphonium or tetraphenylphosphonium bromides takes place through addition of the t-butyl group on a benzene ring at the position para to the phosphorus atom, the ylid formed reacts in a characteristic Wittig reaction with p-tolylaldehyde.     

Regioselective synthesis of β-fluoro-α,β-unsaturated ketones by the reaction of β-diketones with DFMBA

The deoxyfluorination reaction of β-diketones with N,N-diethyl-α,α-difluoro-m-methylbenzylamine (DFMBA) gave β-fluoro-α,β-unsaturated ketones in good yields. The reaction proceeded regioselectively, and only one regioisomer was obtained from the unsymmetrical 1-aryl-1,3-diketones. The reaction is applicable to diketones with a trifluoromethyl group, obtaining good yields of 3,4,4,4-tetrafluorobutenones. We used the resulting β-fluoro-α,β-unsaturated ketones for the reaction with lithium dialkyl cuprates.     

Asymmetric Mannich reaction catalyzed by N-arylsulfonyl-l-proline amides

Proline-derived N-sulfonylcarboxamides efficiently catalyze the asymmetric Mannich reaction of cyclic ketones with N-(p-methoxyphenyl)-protected iminoglyoxylate. Both classical organic solvents and ionic liquids were used as the reaction media. With cyclohexanone, the reaction proceeded with high enantioselectivity (99% ee). Enamine intermediates were investigated by DFT calculations.     

Polysubstituted 2,3-dihydrofuro[2,3-b]pyridines and 3,4-dihydro-2H-pyrano[2,3-b]pyridines via microwave-activated inverse electron demand Diels-Alder reactions

Polysubstituted 2,3-dihydrofuro[2,3-b]pyridines and 3,4-dihydro-2H-pyrano[2,3-b]pyridines have been synthesized from 1,2,4-triazines using the inverse electron Diels-Alder reaction. For this purpose, 3-methylsulfanyl-1,2,4-triazines were reacted with several nucleophiles allowing the formation of appropriately substituted alkynes to undergo the intramolecular inverse electron demand Diels-Alder reaction. Sealed-tube microwave activation of the cycloaddition reaction has proved to be very efficient and allowed shorter reaction times. This strategy enabled an efficient synthesis of 3-hydroxy-2,3-dihydrofuro[2,3-b]pyridines and 4-hydroxy-3,4-dihydro-2H-pyrano[2,3-b]pyridines with several points of diversity on the bicyclic scaffold.     

Preparation of cis-2-aminocyclopropanol: [2+1] cycloaddition reaction of bis(iodozincio)methane with α-ketoimine

A reaction of α-ketoimine with bis(iodozincio)methane gave a cis-2-aminocyclopropanol derivative via [2+1] cycloaddition. The reaction proceeded via a sequential nucleophilic attack of bis(iodozincio)methane to a couple of carbonyl groups in the substrate, which was fixed into s-cis conformation with a couple of zinc atoms in the reagent. The reaction proceeded with high diastereoselectivity.     

Convenient synthesis and unusual reactivity of 2-oxo-2H,5H-pyrano[3,2-c]chromenes

The reaction of 4-oxo-4H-chromen-3-carbaldehydes with coumarin-4-acetic acids under the Perkin conditions follows an interesting pathway that involves aldol reaction and subsequent intramolecular lactonization to afford 2-oxo-2H,5H-pyrano[3,2-c]chromene skeleton. In contrast to chromone-3-carbaldehydes, the same reaction with chromone-2-carbaldehydes yielded only the aldol condensation product. The reaction was performed under thermal and microwave conditions. The reactivity of 2-oxo-2H,5H-pyrano[3,2-c]chromenes in water, alcohol and acetic acid was described.     

Isocyanide based multicomponent reactions of oxazolidines and related systems

N-Alkyloxazolidines react in a multicomponent reaction with carboxylic acids and isocyanides to give N-acyloxyethylamino acid amides. The previously reported reaction conditions were improved using a design of experiments approach (DoE). Under the optimised conditions, good yields of the N-acyloxyethylamino acid amide products are obtained both via a three- or four-component approach from N-alkylethanolamines, aldehydes/ketones, isocyanides and carboxylic acids. The reaction of oxazolidines without a nitrogen substituent was found to give either the expected Ugi products or the N-acyloxyethylamino acid amides depending on the choice of reaction conditions. Optimised reaction conditions were also developed for the ring-expansion of oxazolidines to morpholin-2-ones via reaction with an isocyanide followed by hydrolysis. The mechanistic pathway of the multicomponent reaction was briefly investigated using an ¹⁸O labelling experiment. The carboxylic acid component can be replaced by a range of other acidic nucleophiles including thiobenzoic acid, thiophenol or 5-phenyltetrazole, which are incorporated via an alternative pathway. These latter reactions can also be applied to 2-aminotetrahydrofurans, 2-aminotetrahydropyrans or 4-hydroxybut-2-one, further extending the structural diversity of the multicomponent reaction products.