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The recent years have witnessed the development of metal-catalyzed reductive carboxylation of organic (pseudo)halides with CO2 as C1 source, representing potential powerful alternatives to existing methodologies for preparing carboxylic acids, privileged motifs in a myriad of pharmaceuticals and molecules displaying significant biological properties. While originally visualized as exotic cross-coupling reactions, a close look into the literature data indicates that these processes have become a fertile ground, allowing for the utilization of a variety of coupling partners, even with particularly challenging substrate combinations. As for other related cross-electrophile scenarios, the vast majority of reductive carboxylation of organic (pseudo)halides are characterized by their simplicity, mild conditions, and a broad functional group compatibility, suggesting that these processes could be implemented in late-stage diversification. This perspective describes the evolution of metal-catalyzed reductive carb...

Sulfonyl indoles, as well as related azolyl derivatives, have been recently introduced in synthesis as stable precursors of reactive indolenine intermediates. This personal account reports on the discovery of sulfonyl azoles and their practical utilization in many synthetic processes for the preparation of functionalized 3-substituted indoles, indazoles, and pyrroles. The indolenine intermediates obtained by treatment of sulfonyl azoles with Bronsted bases or Lewis acids can be considered as vinylogous imino derivatives that can be made to react with different nucleophilic reagents. These include organometallic reagents, reducing agents, stabilized carbanions, and heteronucleophiles. The controlled and mild conditions for the generation of indolenines from sulfonyl azoles make these substrates particularly useful in asymmetric synthesis, exploiting organo- or metal-catalyzed processes. Although less exploited, sulfonyl indoles can also be involved in photochemical processes for the preparation of polycyclic derivatives.

Aniline substrates such as (I) and (V) bearing a terminal acetylene at the phenoxy part are suitable for the preparation of the target compounds in the presence of CO and alcohols under conditions A).

This review article reports new procedures and practical application of the nitro to carbonyl conversion that appeared in the literature after our comprehensive report published in 2004. Beside traditional and well explored reactant systems, new procedures including the utilization of molecular oxygen and photoredox catalysis have been introduced for the Nef reaction. Of notable interest is the utilization of the nitro to carbonyl conversion in tandem and cascade processes aimed at the preparation of hetero and carbocyclic derivatives.

The conversion of a wide variety of aryl substituted alkynes provides predominantly 5-, 6-, or 7-membered silylvinylation products.

α-Acryloylamidoalkyl sulfones are converted with in situ generated allylzinc bromides to give a range of dienic products.

Dihydrogen tetrametaphosphate [P4O12H2](2-) (1) can now be synthesized and isolated as its PPN salt ([PPN](+) = [N(PPh3)2](+)) via treatment of [PPN]4[P4O12] with trifluoroacetic anhydride in wet acetone; this simple procedure affords the oxoacid salt in 94% yield. A pKa of 15.83 ± 0.11 in acetonitrile was determined. [P4O12H2](2-) reacts with the dehydrating agent N,N'-dicyclohexylcarbodiimide to afford tetrametaphosphate anhydride [P4O11](2-) (2) in 82% yield, also as the PPN salt. From 2 a monohydrogen tetrametaphosphate ester [P4O10(OH)(OMe)](2-) (3, 96%) was derived by addition of methanol, illustrating that 2 can function as a reagent for chemical phosphorylation. Addition of water to 2 regenerates 1 quantitatively. Deprotonation of 1 by metal amides in the +2 oxidation state led to the unconventional monomeric tin(II) κ(4) tetrametaphosphate [Sn(P4O12)](2-) (4, 78%, a molecular analog of SnO) and binary dimeric chromium(II) bis(μ2,κ(2),κ(2)) derivative [Cr2(P4O12)2](4-) (5, 82%). Structural data stemming from single-crystal X-ray diffraction studies for the PPN salts of anions 1-5 are also reported.

The synthesis of the title compound classes can be achieved from a wide variety of readily available alkynylbenzamides.

D-Galactofuranose (D-Galf) is present in glycoconjugates of several pathogenic microorganisms but is absent in mammals, so it is a good target for the development of chemotherapeutic agents for the treatment of microbial infections. This fact has increased interest in the synthesis of D-Galf-containing molecules for corresponding glycobiological studies. The synthesis of oligosaccharides, glycoconjugates, and mimetics of D-Galf requires specific methods for the preparation of galactose derivatives in the furanosic configuration, the synthesis of appropriate acceptors, and efficient glycosylation methods for the construction of α- and β-D-Galf linkages. This review summarizes the different strategies developed for the preparation of partially protected derivatives of D-Galf, suitable as acceptors for the construction of (1→2), (1→3), (1→5), and (1→6) link- ages, and describes recent applications.

The review describes the flourishing synthesis and brief structure-anti-HIV-1 activity relationships of 6-(arylmethyl)pyrimidin-4(3H)-one derivatives.

The first examples of dihydro-1H-benzindoles by enantioselective γ-lactamization reaction of naphthyl sulfilimines with trichloroacetyl chloride in the presence of ZnCu as catalyst (≥98:2 er and 65–80% yields) are described. Products are obtained by [3,3]-sigmatropic rearrangement of the azasulfonium enolate or followed by a second allylic rearrangement that transfers chirality. The absolute stereochemistry was confirmed by X-ray crystallography, which provides support for the mechanisms proposed.

The photochemical synthesis of benzo[a]carbazoles from easily synthesizable 2-aryl-3-(1-tosylalkyl)indoles is presented. Irradiation of these substrates in polar aprotic solvents (acetone or THF) gives selectively the target products in satisfactory yields. This versatile and efficient procedure promises to be a useful alternative to the multistep strategies reported in the literature.

A three-component coupling of two different benzazole compounds with p-toluenesulfinic acid allows the efficient preparation of unsymmetrical arylsulfonyl bisbenzazole derivatives. Substitution of the arylsulfonyl group from these adducts using sodium borohydride leads to the corresponding bisbenzazoles. Functional implementation of the bisbenzazole system can be achieved using Grignard and Reformatsky reagents.

A convenient synthesis of 4-(1,2,3-triazolylalkyl)-1,2,3-triazole fused dihydroisoquinolines and dihydroisoindoles is reported, starting from easily available (2-iodoaryl)alkyl azides and terminal alkynols. The procedure is based upon transition-metal catalyzed coupling reactions followed by iterative cycloaddition reactions.

Reduction of ketosulfonyl indoles such as (I) or (III) with sodium borohydride allows the entry to tryptophols in a regiocomplementary fashion with respect to the traditional oxirane ring-opening by indoles under Friedel—Crafts conditions.

Cinchona alkaloid-catalyzed reaction of a diversity of in situ generated alkylideneindolenines with various nitroalkanes provides access towards polysubstituted nitroethylindoles, e.g. (III), (V), (VII), (IX) and (XI).

The nitrene transfer reaction from N-tosylimino(phenyl)iodinane (II) towards olefins (I), (IV) and from chloramine-T (VII) towards cyclic ethers (VI) is catalyzed by dinuclear Cu—NHC complexes.

The chapter reports the basic principles of heterogeneous photocatalysis together with a brief presentation of the types of membranes and membrane operations most widely used in this type of application. Coupling the two technologies with the aim of obtaining synergistic effects for conversion in liquid–solid systems is discussed and the relevant papers together with some case studies in pollutants abatement and reaction of synthesis are highlighted.

The potential energy surfaces for a series of metal-assisted reactions have been investigated in the framework of density functional theory (DFT). The reported examples are representative of the difficulties encountered in the construction of reliable potential energy surfaces (PESs) when metal-containing systems are involved. The results contribute to the elucidation of the elementary mechanisms underlying the activation processes of prototypical bonds in gas phase and in enzymatic environment. Keywords: PES; DFT; transition-metal cations; actinides; monoxide cations; enzymes

The removal of the 3-arylsulfonyl group of pyrroles can be achieved under basic or acidic conditions to give vinylogous imino-like derivatives.

Reaction of sulfonylindoles with protected β-nitro ketones affords the corresponding 3-(2-nitroalkyl)indoles that, under acidic conditions, undergo a sequence of cascade processes finally leading to unsymmetrical 1,4-disubstituted carbazoles.

Oxidation of α-amidoaryl sulfones with m-chloroperoxybenzoic acid under mild conditions readily provides the corresponding imides in satisfactory yields. The overall process probably involves formation of an N-acyliminium ion intermediate, which by attack of the peroxyacid anion generates the final imido derivatives.

The alkylation of 5-alkyl-6-(2,6-dihalobenzyl)-2-thioxo-2,3-dihydropyrimidin-4(1H)-ones with MeI, AllSCH2Cl, and MeSCH2Cl in the K2CO3–DMF, NaOMe–MeOH, and KOH–EtOH systems was investigated. A hypothetical mechanism for the reaction is examined, and an explanation is proposed for the composition of the reaction products. The presence of high anti-HIV-1 activity was established in the obtained derivatives of 2-{[(allylsulfanyl)methyl]sulfanyl}pyrimidin-4(3H)-one.

Diethyl phosphite (II) and diphenylphosphine add to a series of unsaturated derivatives using CaO as basic promoter under solventless conditions.

On addition of either BF3·Et2O or H2SO4 the valence photoisomerization of 2-methoxytropone (1) in CH3CN is diverted from 1-methoxy-(2) to 3-methoxybicyclo[3.2.0]hepta-3,6-dien-2-one (3) as products whereas with tropone there is a change from photodimerization to valence isomerization to give cleanly bicyclo[3.2.0]hepta-3,6-dien-2-one (5).

Nouvelle synthese de nitrones par reaction d'un chlorure d'allylmagnesium sur des nitroarenes via addition sur le groupe nitro. Traitement de la mixture par LiAlH 4 en presence de 10% de Pd/C comme catalyseur. Obtention de N-allylanilines

The X-ray molecular structure of naltrexone malonate [(C20H24NO4)+(C3H3O4)–] was determined. In the T-shape molecule, the D and E rings adopt a chair conformation. Ring B is enveloped (Cs). The configuration of the N-cyclopropylmethyl group is equatorial. The preferred conformations and the energetics of the conformational processes of naloxone and naltrexone, as non-protonated (NLX and NTRX) and protonated (NLXH+ and NTRXH+) species, were studied using semiempirical MO calculations of the AM-1 type. The solid-state conformations about the N-substituent groups were not retained in calculations for isolated molecules. The NTRXH+ species was more conformationally restricted than was NLXH+ about the N–C(17) and, especially, C(17)–C(18) bonds. The conformational isoenergy maps calculated for NLX and NTRX showed that the energy barriers were lower, and that the minima zones were larger and shallower with respect to the cationic species. The present findings provided some insights into the possible conformation–activity requirements for µ-pure opioid antagonists.

Homologation of the lactone 14 easily obtained from D-xylose afforded the pyranone 15, a key chiral synthon for the lactone portion of mevinic acids.

Potassium 2,4-pentanedionate reacts with diazosulfides (E)-1 and (Z)-2 in DMSO to give 3-aryl-2,4-pentanediones 3 via an S RN 1 process. Advantages and drawbacks of such new access to 3 are reported together with relevant mechanistic implications.

ω-Nitroalcohols have been prepared by a new and efficient chemio- and regioselective reductive cleavage performed on 2-nitrocycloketones with sodium borohydride in acetonitrile / water. This reaction opens a more practical and convenient route to the synthesis of spiroketals.

(E,E)-1,4-Bis(diethylamino)-2,3-dinitro-1,3-butadiene ( 2a ), obtained from the ring-opening of 3,4-dinitrothiophene, reacts with Grignard reagents in THF to give good yields of 1,4-disubstituted ( Et, cy-Hex, Ph ) 2,3-dinitro- 1, 3-butadienes ( 3a –c) having almost exclusively (E,E) configuration.

The ortho -arylation of phenols by (2-cyanoaryl)azo t -butyl (or phenyl) sulfides in S RN 1 conditions, followed by a silica-gel-catalysed lactonisation of the resulting 2-cyano-2′-hydroxybiphenyls, leads to dibenzo[ b,d ]pyran-6-ones.

Reaction of optically active nitroalkanes with allyl Grignard reagents affords E-Z mixtures of nitrones which can be reduced to chiral hydroxylamines and amines.

The reaction of ortho-substituted nitrobenzenes with 3 mol vinylmagnesium halides gives mainly 7-substituted indoles together with minor amounts of the aniline from complete reduction of the nitroarene. Under the same experimental conditions, para-substituted nitrobenzenes essentially lead to the corresponding anilines, with indoles being recovered in very low yield. Nitrosoarenes react with 2 mol Grignard reagent to give almost the same product distribution. An accurate analysis of the stoichiometry of the reaction established that in the first stage of the reaction nitroarenes are attacked at the oxygen atoms and are reduced to nitrosoarenes via enolate elimination. The nitroso derivative can undergo a 1,2-addition to give an N-aryl-N-vinylhydroxylamino magnesium salt. Hydrolysis of this intermediate affords hydroxylamine and the carbonyl derivative corresponding to the vinyl Grignard reagent, as proved by the reaction of nitroarenes with 2 mol Grignard reagent. In the presence of an excess of vinyl magnesium halide, a complete reduction to vinylaniline derivatives, which hydrolyse to aniline, occurs. The effect of the bulkiness of the substituent both in the nitroarene and in the Grignard reagent, the orientation of alkylation and the relative reaction rates of indole and aniline formation suggest that indoles arise via a completely different route: i.e. an inverse 1,2-addition to the NO double bond. The N-aryl-O-vinylhydroxylamino magnesium salt intermediate can undergo a [3,3]-sigmatropic rearrangement followed by a rapid ring closure. The third mole of Grignard reagent acts as a base on this bicyclic intermediate, re-aromatizing the six-membered ring. Elimination of water ultimately leads to the indole.