First syntheses of 2-hydrogeno-2-oxo-1,4,2-oxazaphosphinanes via intramolecular esterification

Synthesis of 2-hydrogeno-2-oxo-1,4,2-oxazaphosphinanes via either intramolecular transesterification, using potassium tert-butylate as catalytic agent, or phosphinic acid esterification, is described for the first time.     

Synthesis of 2-phenoxyl-2-oxo-1,4,2-oxazaphosphinanes from a three component reaction

Abstract

A one-pot synthetic strategy was developed for the synthesis of heterocyclic 1,4,2-oxazaphosphinanes via a three component Kabachnik-Fields reaction of 2-aminophenol, diphenyl H-phosphonate and carbonyl compounds. Through this newly developed method, 12 organophosphorus heterocycles and 2 related chrysin derivatives were synthesized with high yields. The target compounds were characterized by ¹H, ³¹P and 13C NMR and MS.     

Diastereoselective addition of 2H-2-oxo-1,4,2-oxazaphosphinanes to aldehydes and imines

[reaction: see text] Diastereoselective additions of 2-hydrogeno-2-oxo-1,4,2-oxazaphosphinanes to aldehydes and imines are described. alpha,alpha'-Diaminophosphinic and alpha-amino-alpha'-hydroxyphosphinic derivatives were obtained with de's ranging from 24 to 90%.     

A convenient synthesis and spatial structure of 2-aryl-2-oxo-2-phenylbenzo[e]-1,4,2-oxazaphosphinanes

Phosphorylation of 2-arylideneaminophenol with dichlorophenylphosphine in the presence of triethylamine and subsequent treatment with water led to stereoisomeric derivatives of 3-aryl-2-oxo-2-phenylbenzo[e]-1,4,2-oxazaphosphinanes, which were separated by column chromatography to the individual diastereomers. The structure of stereoisomers was established by NMR spectroscopy and X-ray crystallography.     

Chiral phosphinyl analogues of 2-C-arylmorpholinols: 2-aryl-3,5-diphenyl-[1,4,2]-oxazaphosphinanes

(2R,3R,5R)-2-Aryl-3,5-diphenyl-[1,4,2]-oxazaphosphinanes 6, analogues of C-arylmorpholinol 3, were prepared with diastereomeric excess higher than 94%, via a three step sequence: (i) diastereoselective addition–cyclization reaction from methyl hypophosphite and a chiral imine 10, (ii) pallado-catalyzed arylation, and then (iii) a selective inversion of configuration at the phosphorus center.     

Diastereoselective Michael addition of 2H-2-oxo-1,4,2-oxaza phosphinanes to olefins

Diastereoselective Michael additions of 2-hydrogeno-2-oxo-1,4,2-oxazaphosphinanes to olefins were described. Phosphinopeptide compounds were obtained in very good yield (up to 90%) and diasteromeric excesses ranging from 26 to 78%.     

Phosphinyl analogues of hydroxybupropion: (±)-2-aryl-3,3,5,5-tetramethyl-[1,4,2]-oxazaphosphinanes

Analogous structures in phosphinate series of hydroxybupropion 2, that is, (±)-2-aryl-3,3,5,5-tetramethyl-[1,4,2]-oxazaphosphinanes 8, are prepared according to a two step sequence: addition-cyclization reaction from methyl hypophosphite and oxazolidine 6, followed by a pallado-catalyzed arylation of P-H bond from oxazaphosphinane 7.     

Synthesis of fluorinated 2-oxo-1,4,2-oxazaphosphol-4-ines and their opening by alcohols

Trifluoromethyl-substituted 1,4,2λ⁵-oxazaphosphol-4-ines from phosphorus dichlorides and N-acylimines of hexafluoroacetone have been synthesized and characterized by ¹H, ¹⁹F, and ³¹P NMR. Alcohols open these oxazaphospholines at the P–O bond, forming the corresponding esters.     

One-pot regioselective vinylation of tetrazoles: preparation of 5-substituted 2-vinyl-2H-tetrazoles

The one-pot regioselective preparation of 5-aryl/alkyl-2-vinyl-2H-tetrazoles from 5-substituted tetrazoles via a very simple procedure using 1,2-dibromoethane and triethylamine without the need of any catalyst is described. The mechanism of this reaction is also discussed.     

Direct arylation for the synthesis of 2-arylquinolines from N-methoxyquinoline-1-ium tetrafluoroborate salts and arylboronic acids

A rapid and direct arylation reaction of N-methoxyquinoline-1-ium tetrafluoroborate derivatives and arylboronic acids with high regioselectivety at room temperature was discovered. The reaction shows exceptional functional group tolerance and broad substrate scope regarding both the quinoline derivatives and the arylboronic acids.     

Solid phase synthesis of 6-acylamino-1-alkyl/aryl-4-oxo-1,4-dihydrocinnoline-3-carboxamides

6-Acylmino-1-alkyl/aryl-4-oxo-1,4-dihydrocinnoline-3-carboxamides were synthesized in parallel from 6-nitro-4-oxo-1,4-dihydrocinnoline-3-carboxylic acid. The latter formed amides with amines bound to polystyrene-based resins via acid-labile linkers. N1 and N2-alkylation, followed by alkyl migration yielded only N1-alkylated products. Reduction of the 6-nitro group and acylation concluded the synthesis.     

Synthesis of 1,4,2-dioxaphosphepanes by the reaction of 2-fluoroalkoxy-4-oxo-5,6-benzo-1,3,2-dioxaphosphorinanes with chloral

The reaction of 2-fluoroalkoxy-5,6-benzo-1,3,2-dioxaphosphorinanes with chloral leads to the formation of ring expansion products with a P-C bond, namely, 2-fluoroalkoxy-2,5-dioxo-3-trichloromethyl-6,7-benzo-1,4,2-dioxaphosphepanes with high stereoselectivity.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1676–1678, July, 1991.     

Cu(OAc)2·H2O-catalyzed N-arylation of nitrogen-containing heterocycles

In the absence of any additional ligands, the efficient N-arylation of nitrogen-containing heterocycles with aryl iodides catalyzed by relative low catalyst amount of Cu(OAc)₂·H₂O was developed. This simple catalytic system is involved in the C-N cross-coupling reaction and works for a variety of pyrazole, pyrrole, imidazole, triazole, indole, benzoimidazole, benzotriazole, carbazole, and anilines as well as aryl iodides with different electronic properties. Highly efficient copper(II)-catalyzed N-arylation protocol was established.     

Decarboxylative cross-couplings of 2-aminopyrimidine-5-carboxylic acids

Decarboxylative CC cross-couplings of 2-aminopyrimidine-5-carboxylic acids under a Pd/Ag-based catalytic system opens a new platform for the introduction of diverse C5 substituents. The reaction methods proceeded efficiently with a wide range of the acids and the coupling partners of aryl iodides, alkenes, bromoalkynes, and azoles. Considering ready availability of 2-aminopyrimidine-5-carboxylic acid from the oxidative dehydrosulfurative CN cross-coupling of the 3,4-dihydropyrimidin-1H-2-thiones, this reaction method unambiguously pave a shortcut to densely substituted 2-aminopyrimidine derivatives with unprecedented diversity.     

X-ray diffraction study of bisphosphonate metal complexes: Mg,Sr and Ba complexes of (dichloromethylene)bisphosphonic acid P,P′-dibenzoyl anhydride

The first alkaline earth metal complexes of a dibenzoyl derivative of clodronic acid were prepared and characterised by X-ray crystallography, elemental analysis and infrared spectroscopy. The complexes were [Mg{[Cl₂C(PO₂O(C(O)C₆H₅))₂](H₂O)₅} · H₂O] (1), [Sr₂{[Cl₂C(PO₂O(C(O)C₆H₅))₂]₂(H₂O)₉} · H₂O]_n (2) and [Ba{Cl₂C(PO₂O(C(O)C₆H₅))₂}(H₂O)₂]_n (3). The monomeric units of 1 and the polymeric chains of 2 and 3 form 2D layer-like structures through intermolecular hydrogen bonds. The Cl₂C(PO₂O(C(O)C₆H₅))₂²⁻ ligand acts as a bridging and chelating ligand, forming six- and eight-membered chelate rings with metal atoms. In addition, the previously determined polymeric calcium complex of clodronate, [Ca₂{Cl₂C(PO₃)₂}(H₂O)₆ · 4.5H₂O]_n(4), was synthesised by hydrolysis method from the dibenzoyl derivative of clodronic acid.     

Direct ortho-arylation of 2-arylbenzoxazoles via C-H activation

A new and highly regioselective arylation of 2-arylbenzoxazoles based on C-H activation has been developed. The results represent the first examples of palladium-catalyzed direct ortho-arylation of 2-arylbenzoxazoles and also provide a facile route for the synthesis of complicated structures containing arylated benzoxazoles moieties.     

Mn(OAc)3*2H2O promoted addition of arylboronic acids to quinoxalin-2-ones

A simple method has been developed for the synthesis of 3-aryl quinoxalin-2-one derivatives through an oxidative cross-coupling of arylboronic acids with quinoxalin-2-ones using a readily available oxidant Mn(III) acetate dihydrate. This method provides 3-aryl quinoxalin-2-one scaffolds with a broad substrate scope.