Efficient solid-phase synthesis of 1,3,5-trisubstituted 1,3,5-triazine-2,4,6-triones

The solid-phase synthesis of 1,3-disubstituted and 1,3,5-trisubstituted 1,3,5-triazine-2,4,6-triones from MBHA and Wang resin is described. Reaction of resin-bound amino acids with isocyanates yield resin-bound ureas, which further react with chlorocarbonyl isocyanate in toluene at 65 degrees C to selectively afford the resin-bound 1,3-disubstituted 1,3,5-triazine-2,4,6-triones. Selective alkylation at the N-5 position of the resin-bound 1,3-disubstituted 1,3,5-triazine-2,4,6-triones was accomplished by treatment with alkyl halides in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU). The desired products were cleaved from their solid support and obtained in good yield and purity. The method can be employed in production of toltrazuril analogue libraries for identification of new anticoccidial agents.     

A versatile method for carbon-nitrogen bond formation via ene reactions of acylnitroso compounds

The use of acylnitroso compounds of the general formula RCONO as enophiles in the formation of carbon-nitrogen bonds is described. Both inter- and intramolecular ene reactions have been studied. For the intermolecular examples, nitrosocarbonylmethane, thermally liberated from its Diels-Alder adduct with 9,10-dimethylanthracene, is reacted with various olefins giving the corresponding N-alkylhydroxamic acids in moderate to high yields, providing an efficient method for allylic amidation. The regiochemistry of the intermolecular reaction is observed to be the result of kinetic control, and the direction of addition is consistent with attack by the olefin on electron-deficient nitrogen. Several examples of intramolecular ene cyclization are demonstrated, providing efficient entry into both spiro and fused bicyclic nitrogen containing systems which can be viewed as derived from annulation of 5- and 6- membered nitrogen containing rings onto 5- and 6-membered carbocycles, respectively. Various examples of this hetero-annulation scheme are described. Experimental details are also privided describing typical reaction procedures.     

Palladium-catalyzed C-C bond formation of arylhydrazines with olefins via carbon-nitrogen bond cleavage

The unactivated carbon-nitrogen bond of various aryl hydrazines was cleaved under very mild conditions by Pd(0) with the assistance of Pd(II). The in situ generated aryl palladium complex readily takes part in the C-C bond formation with olefins. This study offered a new mode of C-Pd bond formation, which will spur the development of palladium-catalyzed cross-coupling in the future.     

Molecular quadrupole moments and magnetic anisotropies of non-dipolar 1,3,5-trisubstituted benzenes

The molecular quadrupole moments and magnetic anisotropies of a series of non-dipolar 1,3,5-trisubstituted benzenes (C₆H₃X₃; X=H, Me, t-Bu, F, Cl, Br) are analysed to obtain information concerning the charge distributions. Whereas alkyl groups have relatively little effect on benzene. halogen substituents are strongly interactive and the moments become progressively less negative from 1.3.5-tribromo-to 1.3.5-trifluoro-benzene.     

Linear heterocyclic aromatic fluorescence compounds having various donor-acceptor spacers prepared by the combination of carbon-carbon bond and carbon-nitrogen bond cross-coupling reactions

A family of novel linear 1,10-phenanthroline-based (A-D-A-D-A) and oligothiophene-based (A-D-D-D-(D)-A) heterocyclic aromatic fluorescence compounds having N-containing imidazole and pyridine tails with effective π-conjugated systems, prepared by the combination of carbon-carbon (C-C) bond and carbon-nitrogen (C-N) bond cross-coupling reactions, is described. They have molecular lengths of more than 2.30 nm in the cases of 4, 6, 9, and 26, various D-A spacers, and certain N-coordination sites (phen, imidazole, and pyridine). X-ray single-crystal structures of 13 compounds reveal a variety of trans and cis configurations with different dihedral angles between adjacent aromatic heterocycles. Synthetic, computational, and spectral studies have been made to reveal the differences between cross-coupling approaches on the C-C bond and C-N bond formation as well as band gaps and energy levels and optical and electrochemical properties for related compounds. The influences of introducing a β-methyl group to the thiophene ring on reaction activity, solubility, and conformation of related compounds have also been discussed.     

Direct carbon-carbon bond formation via soft enolization: a facile and efficient synthesis of 1,3-diketones

Ketones undergo soft enolate formation and acylation on treatment with MgBr(2).OEt(2), i-Pr(2)NEt, and various acylating agents to give 1,3-diketones. The process is particularly efficient for N-acylbenzotriazoles and O-Pfp esters, and, in these cases, is conducted with untreated, reagent-grade CH(2)Cl(2) open to the air, thus providing an exceptionally simple approach to the synthesis of this important class of compounds.     

Iron-catalyzed synthesis of glycine derivatives via carbon-nitrogen bond cleavage using diazoacetate

Treatment of tertiary amines with diazoacetate in the presence of a catalytic amount of an iron salt, FeCl(3), in ethanol gave glycine derivatives. In this reaction, a carbon-nitrogen single bond of the amine was cleaved.     

Oxidative carbon-carbon bond formation via silyl bis-enol ethers: controlled cross-coupling for the synthesis of quaternary centers

Unsymmetrical silyl bis-enol ethers have been developed as effective substrates for synthesizing quaternary centers from tetralone derivatives through oxidative carbon-carbon bond formation. The derived products are shown to be highly versatile intermediates that may be used to generate diverse structures such as cyclopentenones, 2H-pyrroles, and spirocyclic pyrrolidines.     

Carbon-silicon and carbon-carbon bond formation by elimination reactions at metal N-heterocyclic carbene complexes

Two functional groups can be delivered at once to organo-rare earth complexes, (L)MR(2) and (L)(2)MR (M = Sc, Y; L = ({1-C(NDippCH(2)CH(2)N)}CH(2)CMe(2)O), Dipp = 2,6-(i)Pr(2)-C(6)H(3); R = CH(2)SiMe(3), CH(2)CMe(3)), via the addition of E-X across the metal-carbene bond to form a zwitterionic imidazolinium-metal complex, (L(E))MR(2)X, where L(E) = {1-EC(NDippCH(2)CH(2)N)}CH(2)CMe(2)O, E is a p-block functional group such as SiR(3), PR(2), or SnR(3), and X is a halide. The "ate" complex (L(Li))ScR(3) is readily accessible and is best described as a Li carbene adduct, ({1-Li(THF)C(NDippCH(2)CH(2)N)}CH(2)CMe(2)O)Sc(CH(2)SiMe(3))(3), since structural characterization shows the alkoxide ligand bridging the two metals and the carbene Li-bound with the shortest yet recorded Li-C bond distance. This can be converted via lithium halide-eliminating salt metathesis reactions to alkylated or silylated imidazolinium derivatives, (L(E))ScR(3) (E = SiMe(3) or CPh(3)). All the E-functionalized imidazolinium complexes spontaneously eliminate functionalized hydrocarbyl compounds upon warming to room temperature or slightly above, forming new organic products ER, i.e., forming C-Si, C-P, and C-Sn bonds, and re-forming the inorganic metal carbene (L)MR(X) or (L)(2)MX complex, respectively. Warming the tris(alkyl) complexes (L(E))MR(3) forms organic products arising from C-C or C-Si bond formation, which appears to proceed via the same elimination route. Treatment of (L)(2)Sc(CH(2)SiMe(3)) with iodopentafluorobenzene results in the "reverse sense" addition, which upon thermolysis forms the metal aryl complex (L)(2)Sc(C(6)F(5)) and releases the iodoalkane Me(3)SiCH(2)I, again facilitated by the reversible functionalization of the N-heterocyclic carbene group in these tethered systems.     

Catalytic carbon-sulfur bond formation by amphoteric vanadyl triflate: exploring with thia-Michael addition, thioacetalization, and transthioacetalization reactions

A series of thiols have been examined as protic nucleophiles for Michael-type additions to α,β-unsaturated carbonyls as well as double nucleophilic condensations with aldehydes, ketones, and acetals catalyzed by amphoteric, water-tolerant vanadyl triflate under mild and neutral conditions. The newly developed C-S bond formation protocols were carried out smoothly in good to high yields in a highly chemoselective manner.     

Diastereoselective synthesis of branched 2-deoxy sugars via radical c-c bond formation reactions

From glycals 1 and 6, 2-deoxy sugars can be synthesized in 40–72% yields. With 1,2-disubstituted alkenes 3 this radical C-C bond formation reaction leads with high stereoselectivity to the isomers 4 and 8.     

First catalytic asymmetric synthesis of beta-amino-beta-polyfluoroalkyl ketones via proline-catalysed direct asymmetric carbon-carbon bond formation reaction of polyfluoroalkylated aldimines

Proline-catalysed direct asymmetric carbon-carbon bond formation reaction of polyfluoroalkylated aldimines with acetone afforded the corresponding beta-(p-methoxyphenyl)amino-beta-polyfluoroalkyl ketones in high enantioselectivities (up to 98% ee).     

Ruthenium-catalyzed carbon-carbon bond formation between propargylic alcohols and alkenes via the allenylidene-ene reaction

A novel ruthenium-catalyzed carbon-carbon bond formation between propargylic alcohols and alkenes via the allenylidene-ene reaction has been found to afford the corresponding 2,4-disubstituted-1-hexen-5-ynes in moderate yields. The finding described here discloses a new reactivity of allenylidene complexes. As a synthetic application, intramolecular cyclization of propargylic alcohols bearing an alkene moiety has been developed to give the corresponding syn-substituted chromanes in high yields with an excellent diastereoselectivity.     

Remarkably efficient synthesis of 2H-indazole 1-oxides and 2H-indazoles via tandem carbon-carbon followed by nitrogen-nitrogen bond formation

Base-catalyzed tandem carbon-carbon followed by nitrogen-nitrogen bond formations quantitatively converted N-alkyl-2-nitro-N-(2-oxo-2-aryl-ethyl)-benzenesulfonamides to 2H-indazoles 1-oxides under mild conditions. Triphenylphosphine or mesyl chloride/triethylamine-mediated deoxygenation afforded 2H-indazoles.     

Nickel-catalyzed synthesis of 1,3,5-trisubstituted hydantoins from acrylates and isocyanates

One molecule of acrylate reacts with two molecules of isocyanate in the presence of a nickel(0)/SIPr catalyst to give a 1,3,5-trisubstituted hydantoin. Two processes operate in sequence, the first, regioselective formation of N-substituted fumaramate from acrylate and isocyanate and, the second, ring closure of the fumaramate with incorporation of another molecule of isocyanate.     

Stereoselective carbon-carbon bond formation via the Mitsunobu displacement of chiral secondary benzylic alcohols

[reaction: see text] The stereoselective displacement of a variety of chiral benzylic alcohols with triethylmethanetricarboxylate (TEMT) under Mitsunobu conditions (DEAD, PMe(3)) has been demonstrated to proceed in good yield (70-94%) and with a high degree of inversion. Subsequent saponification and decarboxylation of the products thus obtained provide chiral 3-aryl-3-substituted propanoic acids without racemization.