Recent progress on catalytic [1,3]-oxygen rearrangement reactions from nitrogen to carbon atoms

[1,3]-Rearrangement reactions of an oxygen atom from a nitrogen atom to a carbon atom is an ideal way to synthesize highly elaborate molecules in which nitrogen and oxygen functionalities are vicinally arranged. Recently, it has been disclosed that this intriguing transformation takes place in the presence of Lewis acidic metal catalysts. In this digest, we summarize recent findings on the catalytic [1,3]-oxygen rearrangement reactions, such as direct [1,3]-rearrangement of N-oxygenated enamines and anilines, as well as π-acidic metal-catalyzed cascade reaction involving the [1,3]-rearrangement process.     

Palladium(0)-catalyzed rearrangement of allyl enol ethers to form chiral quaternary carbon centers via asymmetric allylic alkylation

Herein we report the first palladium(0)-catalyzed asymmetric allylic alkylation (AAA) of allyl enol ether via π-allylpalladium intermediate using Trost chiral diphosphine. This unprecedented reaction produced very rare α-aryl quaternary aldehydes with multi-functional groups. The main novelty in the chemistry demonstrates that enol ethers can be used as precursors for π-allylpalladium intermediates, an observation that is certainly rare and to the best of our knowledge, perhaps without prior precedent. Chiral ligand (R,R)-L3 was found to be optimal in this Pd-AAA reaction and provided good to excellent yield (80–95%) and enantioselectivity (70–90%) with a range of analogs.     

Nitrosoalkylureas containing quaternary nitrogen atoms. Communication 4. Synthesis of new nitrosoalkylureas from bisquaternary ethylenediammonium salts

Conclusions A method has been developed for the synthesis of new nitrosoalkylureas based on bisquaternary ethylenediammonium salts.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, pp. 610–613, March, 1986.     

Reactions of tautomeric quaternary phosphonium salts based on triphenylphosphine and 3-phenylpropargyl bromide with nitrogen nucleophiles

Triphenyl(3-phenylprop-1-ynyl)phosphonium bromide (3) was isolated. This compound is a third isomer for the tautomeric system triphenyl(3-phenylpropadienyl)phosphonium bromide (1) triphenyl(3-phenylprop-2-ynyl)phosphonium bromide (2). Salts 1 and 2 smoothly react with secondary amines to give adducts with an ,-double bond, while salt 3 changes to an allene ylide. Addition of phenylhydrazine and triphenyl(phenylethynyl)phosphonium bromide to salts 1 and 2 and addition of dimethylformamide to salt 2 were performed.     

Effect of chalcogenyl substituent on the course of allyl rearrangement at chalcogenation of 1,3-dichloropropene

Formation of 1,3-dichalcogenylpropene at the treatment of 1,3-dichloropropene with organic dichalcogenides in a redox system hydrazine hydrate–KOH is governed by the possibility of an allyl rearrangement. In the presence of bases this rearrangement proceeds via carbanion partially stabilized by the chalcogenyl substituent. The effectivity of the stabilization and consequently the probability of the rearrangement varies in the series of substituents PhS > BnS > PhSe. In the stage of the direct nucleophilic substitution of chlorine the anion PhSe^? possesses the highest activity.     

Stereocontrolled one-pot synthesis of cycloalkane derivatives possessing a quaternary carbon using allyl phenyl sulfone

Stereocontrolled one-pot synthesis of cyclopentane derivatives possessing quaternary carbon using allyl phenyl sulfone and epoxyiodide was presented. Furthermore, application of this protocol to the synthesis of cycloalkane derivatives with different ring sizes was successful.     

Nitrosoalkylureas with a quaternary nitrogen. 7. Quantitative relation between decomposition rate and structure of nitrosoalkylureas derived from alkylammonium salts

Conclusions The decomposition rate of the dialkyl-substituted methyl- and cyclohexylnitrosoureas correlates well with the charge on N that does not carry the nitroso group, as calculated by CNDO/2. Here the cyclohexyl residue has a greater destabilizing effect than does the methyl radical.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 798–800, April, 1989.     

Palladium-catalyzed decarboxylative aza-Michael addition-allylation reactions between allyl carbamates and activated olefins. Generation of quaternary carbon adjacent to secondary amine carbon center

The reaction of allyl carbamates with activated olefins in the presence of Pd(PPh3)4 catalyst in THF proceeded smoothly at room temperature to give the corresponding beta,alpha-bisadducts, beta-amino-alpha-allylated products, in high yields. Not only highly activated olefins containing two cyano groups but also 2-cyano enones underwent facile aza-Michael addition--allylation with various allylic carbamates giving the corresponding products in high yields and with high diastereoselectivities. The stereochemistry of the singly formed product was confirmed with the help of X-ray crystallographic technique. It is an excellent method for creating beta-amino alpha-allyl ketones having two contiguous stereocenters: quaternary carbon adjacent to secondary amine carbon center.     

π-Allylmetal chemistry: III. A facile cleavage of allyl groups from quaternary nitrogen by platinum(0) complexes

Reactions of Pt(PPh₃)₂L (I, L = PPh₃; II, L = C₂H₄) with [(CH₂CRCH₂)NH_nEt_{3? n}]X (R = H, n = 0, 1; R = Me, n = 0; X = Cl0₄, BPh₄) in acetone or methylene chloride readily afford the corresponding π-allylplatinum(II) complexes, [Pt(π-C₃H₄R)(PPh₃)₂] X and NH_n Et_{3? n} in good yields. The reactivity patterns in the rapid formation of the π-allyl complexes from II and [(allyl)NH₃]Cl0₄ (allyl = CH₂CHCH₂, CH₂CHCHMe, CH₂CMeCH₂, trans-MeCHCHCH₂) are compared with those in the synthetically equivalent conversion of allylamines to the π-allyl complexes induced by platinum(II) hydrido complexes.     

First anionic silyl migration from sp2 carbon to carbonyl oxygen. Stereospecific allylation of (Z)-beta-trimethylsilyl-alpha,beta-unsaturated ketones

1,4-Silyl migration from sp2 carbon to carbonyl oxygen proceeded by the treatment of (Z)-beta-trimethylsilyl-alpha,beta-unsaturated ketones with copper(I) tert-alkoxide to afford vinylmetal species, which reacted with allylic halides to produce enol trimethylsilyl ethers of beta-alk-2-enyl-alpha,beta-unsaturated ketones with complete retention of configuration.     

Reinvestigation of the stevens rearrangement of 1-benzyl-1,3,4-trimethyl-1,2,5,6-tetrahydropyridinium salts. II. Synthesis of 2-aryl-3-isopropenyl-1,3-dimethylpyrrolidines

cis-2-Aryl-3-isopropenyl-1,3-dimethylpyrrolidines Ha and IIb have been synthesized by an unambiguous way, thus confirming the structure of the methylene derivatives obtained as by-products in the Stevens rearrangement of 1-benzyl-1,3,4-trimethyl-1,2,5,6-tetrahydropyridinium salts Ia and Ib. The synthesis is based on the acid-induced intramolecular cyclization between an iminium salt and the α-position of a ketal group. Thus, condensation between amino ketal XXI, prepared via Gabriel synthesis from 5-chloro-3-methyl-2-pentanone, and the appropriate aldehyde afforded imines XXI. Their treatment with dry hydrogen chloride followed by acid hydrolysis and methylation gave 3-acetylpyrrolidines IV, which were transformed into the isopropenyl derivatives II by reaction with methyl-lithium and further dehydration.     

Synthesis of allylamides from allyl halides, carbon monoxide, and titanium-nitrogen complexes prepared from molecular nitrogen

4-Phenylbut-3-enamide could be synthesized from corresponding 3-chloroprop-2-enylbenzene, carbon monoxide (1 atm), and titanium-nitrogen complexes, prepared from Ti(OⁱPr)₄, Li, TMSCl, and molecular nitrogen (1 atm), using a palladium catalyst. The reaction proceeds via transmetalation of the titanium-nitrogen complex to an acylpalladium complex. P^tBu₃ as a ligand of the palladium catalyst, afforded a good result, and the amounts of Li and TMSCl affected the yield of amide. When the reaction was carried out using a bidentate ligand on the palladium complex under an atmosphere of argon instead of carbon monoxide, an allylamine derivative was obtained.     

Nitrosoalkylureas with a quaternary nitrogen atom 8. Study of reaction kinetics of decomposition in an aqueous medium of nitrosoalkylureas derived from alkanediammonium salts

The reaction kinetics was studied of the decomposition in aqueous medium of nitrosoalkylureas (NAU) with antitumorigenic activity, derived from bisquaternary ammonium salts and tertiary diamine hydrochlorides of the general formula

Aminopentadiene imines from zincke salts of 3-alkylpyridines. Application to a synthesis of pyridinium salts from amino acids

The reaction of Zincke salts with primary amines to give pyridinium salts generally requires rather elevated temperature to go to completion (50-100 degrees C). It is shown that the addition of 1 equiv of a secondary amine allows formation, at ambient temperature, of intermediate aminopentadiene imine salts which can be isolated and were found to cyclize in acidic medium to give pyridinium salts at temperatures which do not exceed 50 degrees C. If this process has a tendency to give lower yields of pyridinium salt than the standard Zincke procedure, it can be advantageous in some cases, as illustrated by the synthesis of pyridinium salts from amino acids, a challenging reaction which does not work starting from Zincke salt in the absence of diethylamine. More generally, the reaction can be extended to primary amines featuring polar functions, as exemplified by a pyridinium salt synthesis (75 degrees C) in 55% yield from l-carnosine.     

Photochemistry of mesoionic compounds. Photochemical conversion of 5-azido-1,3-diaryltetrazolium salts to novel tricyclic mesoions with a tetrazolo[1,5-a]benzimidazole skeleton

A new type of tetrazolium-5-amide mesoions 2 with a tricyclic tetrazolo[1,5-a]benzimidazole skeleton has been synthesized via photolysis of 5-azido-1,3-diaryltetrazolium salts 1 .     

Preparation of 1,3-diols by metalation-hydroboration of alkynes: A 1,2-hydrogen migration from boron to carbon

Metalation of a series of 1- and 2-alkynes with subsequent treatment with diborane and oxidation gave 1,3-diols exclusively. Deuteroboration of the lithiated acetylenes established the occurrence of a displacement of one of the B atoms by deuterium in gem-diboronated compounds. Hydroboration of several acetylenes and acetylides was also studied.