CoI-Catalyzed Barbier Reactions of Aromatic Halides with Aromatic Aldehydes and Imines

The reductive Barbier coupling of aromatic halides and electrophiles has been achieved using a CoBr₂/1,10-phenanthroline catalytic system and over stoichiometric amounts of zinc. The reaction displayed a broad scope of substrates, including (hetero)aryl chlorides as pro-nucleophiles and aldehydes or imines as electrophiles, leading to diarylmethanols and diarylmethylamines in moderate to excellent yields, respectively.     

Reactions ANC Rearangements of Carboxamides Phosphorylated by Tervalent Phosphorus Chlorides

Abstract

We have found that N-substituted amides of carboxylic or thiocarboxylic acids (I) react with tervalent phosphorus chlorides to give N- and O(S)-phosphorylated derivatives (II) which isomerise into imidoyl(thio)phosphonates (III). The factors determining the ability of the initial products (II) and their iminated derivatives (IV) to participate in diad and triad rearrangements have also been studied.     

Reactions with Hydrophosphoryl Halides

Abstract

In the systems RPCl₂+H₂O, RPCl₂+RCOOH, RPCl₂+RPH(O)OH and RPH(O)OH+RCOX the formation of hydrophosphoryl halides RPH(O)X (X=Cl,Br,I; R=H,OH,Hal,Alk,AlkO,Ar) was proved by spectral and chemical methods. Hydrophosphoryl halides react with alyphatic ketones R′₂CO yielding phosphinic halides R[R′₂C(OH)]P(O)X (X-ray analysis). In case of aromatic aldehydes and ketones containing electron donor substituentes, the addition products are rearranged into α-halogenalkylphosphinic acids.     

Reactions of Elemental Phosphorus and Phosphine with Electrophiles in Superbasic Systems: XV. Phosphorylation of Allyl Halides with Elemental Phosphorus

Elemental phosphorus (red or white) reacts with allyl chloride and allyl bromide in a two-phase system aqueous KOH-organic solvent to form tertiary symmetrical and mixed phosphine oxides among which tris(prop-2-enyl)-, bis(prop-2-enyl)[(E)-prop-1-enyl]-, bis(prop-2-enyl)[(Z)-prop-1-enyl]-, (prop-2-enyl)[(E)-prop-1-enyl][(Z)-prop-1-enyl]-, bis[(E)-prop-1-enyl](prop-2-enyl)-, bis[(Z)-prop-1-enyl](prop-2-enyl)-, tris-[(E)-prop-1-enyl]-, and bis[(E)-prop-1-enyl][(Z)-prop-1-enyl]phosphine oxides were identified. The conditions (room temperature, 60% aqueous KOH-dioxane) allowing preparation from white phosphorus and allyl bromide of tris(prop-2-enyl)- and bis(prop-2-enyl)[(E)-prop-1-enyl]phosphine oxides as major products in the total yield of up to 96% were found.     

Decarboxylative Mannich Reactions with N-Alkyl Imines

The use of N-alkyl imines in decarboxylative Mannich reaction with substituted malonic acids half oxyesters (SMAHOs) has been developed to afford a direct access to secondary β^2,3-aminoesters. The transformation occurs under very practical conditions (DABCO as a catalyst in bulk toluene and open to air) and can be performed with a broad range of each substrate in yields of 36 to 97 %. Importantly, the reaction was found to require the use of acidic additives in combination with the organocatalyst to limit the competitive olefination reaction.     

Phosphorylation of Allyl Halides with White Phosphorus

White phosphorus reacts with allyl bromide in the system KOH-dioxane-H 2 O at room temperature to form tris(propen-2-yl), bis(propen-2-yl)(E-propen-1-yl), and bis(E-propen-1-yl)(propen-2-yl)phosphine oxides in a total quantitative yield, their molar ratio being 1:0.5:0.1.     

Reactions of Aromatic Aldehydes with Boron Halides

Recently, during studies directed toward the total synthesis of the antibiotic frustulosin 1^1,2 we encountered some problems in the removal of methoxyl groups during the preparation of the phenolic aldehyde 2. Our efforts to effect this transformation led us to investigate the reactions of the boron trihalides with aromatic aldehydes. Although the methoxyl group has many desirable properties for hydroxyl protection its stability to both acids and bases often presents difficulties at the time of removal. Of the many reagents and methods devised³ for the removal of methoxyl and other alkoxyl groups boron tribromide can be considered as one of the most widely applicable reagents for this purpose. However, as a fairly powerful Lewis acid, complications can arise when acid.     

Reactions of Dimethoxycarbene with N‐Tosylated Imines

The reactions of dimethoxycarbene (DMC; 2 ), which was generated in situ by thermal decomposition of 2,5‐dihydro‐2,2‐dimethoxy‐5,5‐dimethyl‐1,3,4‐oxadiazole ( 1 ), with N‐tosylated imines of xanthone and 2,3 : 6,7‐dibenzosuberenone, 3a and 3d , respectively, led to different adducts with rearranged skeletons. In the case of 3a , the 1 : 1 adduct 5 as well as the 2 : 1 adduct 6 were obtained (Scheme 2). The formation of both products can be explained by a migration of a MeO group of the DMC fragment in a zwitterionic intermediate. On the other hand, migration of a Me group of DMC is necessary for the formation of the two 1 : 1 adducts 13 and 14 of 2 and 3d (Scheme 5). The structures of all products have been established by X‐ray crystallography.     

Reactions of Diazo Compounds with Imines. Preliminary communication

The [Rh₂(OAc)₄]-catalyzed addition of methyl diazoacetate to N-benzylideneaniline ( 1a ) afforded the imine cis- 2 in 35% yield. Under catalysis by chiral Rh^II catalysts, however, only racemic 1a was produced, and the yield was low. In the presence of dimethyl maleate, aziridine formation was suppressed, and an intermediate ylide 6 was trapped as cycloadduct 7 . No aziridines were obtained, however, from 1b, 1c , and 3 . The iminium salt 8 reacted with (trimethylsilyl)diazomethane in the absence of [Rh₂(OAc)₄] via dipolar cycloaddition followed by extrusion of N₂ to 10 .     

Study on Unexpected Cycloaddition Reactions of Imines with THF

Thesynthesisofnitrogen-containingheterocylesthroughcycloadditionreactionofimineshasstimulatedmuchpreparativeandmechanisticwork'".Whenweattemptedtosynthesizeapolycycliccompound3byadditionreactionofimineland5-norbornene-2,3-dicarboxylicacid2,however,unexpectedtricycliccompounds4and6wereobtainedinsteadofthedesignedproduct3(Schemcl).Heretetrahydrofuran(THF)servedasthesourceofdihydrofiJranwhichunderwentcycloadditionwithlgiving4and6.Ananalogousreactionwasnotedpreviouslyinthislaboratory'(Scheme2).…     

Fluorinated Imines in Tandem and Cycloaddition Reactions

The chemistry of fluorinated compounds has experienced extraordinary growth in recent decades due to the many and varied properties which many of the compounds that contain fluorinated groups possess. Among all of them, fluorinated chiral imines, in particular the Ellman's imines, are of great importance since they are some of the most interesting building blocks for the synthesis of a large number of enantioenriched carbocycles and heterocycles with extraordinary biological and synthetic properties. This personal account covers the most significant results obtained in our research group in the last two decades concerning asymmetric tandem reactions, paying special attention to the intramolecular aza-Michael reaction (IMAMR), diversity oriented synthesis (DOS), asymmetric tandem reactions involving a p-tolylsulfinyl group as chiral inducer and cycloaddition processes, in particular, the Pauson-Khand reaction, [2+2+2]-cycloadditions and metathesis reactions, starting mainly from enyne compounds and through the use of fluorinated chiral N-sulfinyl imines and their derivatives as starting materials.     

Diverse Reactions of Sulfonyl Chlorides and Cyclic Imines

Abstract

Although alkanesulfonyl chlorides react with linear imines to give rise to β-sultam derivatives, in this study, they were reacted with various cyclic imines, including 1-pyrroline, oxazoline, 5,6-dihydro-4H-oxazines and thiazines, 4,5-dihydro-3H-benzo[c]azepine, and 3,4-dihydroisoquinoline, to produce diverse products instead of β-sultam derivatives. The results indicate that alkanesulfonyl chlorides react with cyclic imines to generate N-alkanesulfonyl cyclic iminium ions, which are attacked by nucleophiles, such as water and chloride anion, in the reaction systems, affording addition products. The iminium intermediates cannot undergo a ring closure to form β-sultam derivatives. Arenesulfonyl chlorides showed similar behavior when they reacted with cyclic imines. The scope and limitation of the reaction between sulfonyl chlorides and imines were investigated.

GRAPHICAL ABSTRACT      

Reactions of Elemental Phosphorus and Phosphines with Electrophiles in Superbasic Systems: XII. Synthesis of Unsymmetrical Tertiary Phosphine Oxides from Red Phosphorus and Organyl Halides

Alkyldibenzyl- and benzyldialkylphosphine oxides were prepared in one stage by direct phosphorylation of a mixture of alkyl bromides and benzyl chloride with red phosphorus under the conditions of phase-transfer catalysis (concentrated aqueous KOH solution-dioxane-benzyltriethylammonium chloride).     

Reactions of O2 --Containing Supramolecules with Alkyl Halides

Formation of O₂ ^--containing supramolecules generated from the system 18-crown-6-KO₂ and electrochemically (tetraethylammonium superoxide) and the kinetics of the reactions of the generated O₂ ^- with alkyl halides in acetonitrile were studied conductometrically and UV-spectrophotometrically; the kinetic parameters of the processes were determined. The E2 mechanism was suggested for the reaction.     

Chemoselective Reactions of Functionalized Sulfonyl Halides

Chemoselective transformations of functionalized sulfonyl fluorides and chlorides are surveyed comprehensively. It is shown that sulfonyl fluorides provide an excellent selectivity control in their reactions. Thus, numerous conditions are tolerated by the SO₂F group – from amide and ester formation to directed ortho-lithiation and transition-metal-catalyzed cross-couplings. Meanwhile, sulfur (VI) fluoride exchange (SuFEx) is also compatible with numerous functional groups, thus confirming its title of “another click reaction”. On the contrary, with a few exceptions, most transformations of functionalized sulfonyl chlorides typically occur at the SO₂Cl moiety.     

Reactions between Triethyl Phosphate and Metal Halides

Triethyl phosphate reacts with M(I), M(II) or M(III) halides at 100–250°C with formation of the following complexes: M[OOP(OC₂H₅)₂]₃, (M ? Al, Ga, In, Sc, Y, Dy, Ti, V, Cr, Fe); M[OOP(OC₂H₅)₂]₂, (M ? Fe, Cu); VO[OOP(OC₂H₅)₂]₂; Li[OOP(OC₂H₅)₂]; M₂[OOP(OC₂H₅)₂]₂ [OOP(OC₂H₅)? O? P(OC₂H₅)OO], (M ? Mn, Co, Ni); and M₃HP₂O₇ (M ? Rb, Cs). These complexes were characterized by means of their infrared and electronic spectra and magnetic susceptibilities.     

Dialkylzinc‐Mediated Cross‐Coupling Reactions of Perfluoroalkyl and Perfluoroaryl Halides with Aryl Halides

A highly chemoselective perfluoroalkylation reaction of aromatic halides is reported. Thermally stable perfluoroalkylzinc reagents, generated by a rapid halogen–zinc exchange reaction between diorganozinc and perfluoroalkyl halide species, couple with a wide range of aryl halides in the presence of a copper catalyst, in moderate to high yields. Good stability of the perfluoroalkylzinc species was indicated by DFT calculation and the reagents were storable for at least three months under argon without loss of activity. This method is applicable to gram‐scale synthesis, and its functional group tolerance compares favorably with reported protocols.