Metalated nitriles: organolithium, -magnesium, and -copper exchange of alpha-halonitriles

[reaction: see text] alpha-Halonitriles react with alkyllithium, organomagnesium, and lithium dimethylcuprate reagents generating reactive, metalated nitriles. The rapid halogen-metal exchange with alkyllithium and Grignard reagents allows selective exchange in the presence of reactive carbonyl electrophiles, including aldehydes, providing a high-yielding alkylation protocol. Lithiated and magnesiated nitriles react with propargyl bromide by S(N)2 displacement whereas organocopper nitriles react by S(N)2' displacement, correlating with the formation of a C-metalated nitrile.     

Oxygen and carbon-acylation of enolates by ketenes

Ketenes react with lithium enolates mainly by O-acylation, thus providing a convenient route to vinyl esters and their enolates.     

Regio- and stereoselective ring-opening reactions of epoxides with indoles and pyrroles in 2,2,2-trifluoroethanol

Aliphatic and aromatic epoxides react regio- and stereoselectively with indoles and pyrroles in 2,2,2-trifluoroethanol without the use of a catalyst or any other additive. While aromatic epoxides are selectively attacked at the benzylic position, aliphatic epoxides react at the less-substituted position. Chiral epoxides react with >99 % ee (ee=enantiomeric excess).     

Olefin addition to acetylated glycals. A new route to C-glycosides.

Olefins react with glycals in the presence of Lewis acids providing a new route to C-glycosides.     

Ruthenium-catalysed ortho alkylation of hydroxyacetophenones; the functionalisation of ring C aromatic diterpenoids

Ortho C-H bond coupling of some 2-alkoxyacetophenones with olefins catalysed by ruthenium complexes results in a high yield of the ortho alkylated product, providing that a suitable protecting group is employed. No such protection was required for a para-alkoxy group; an activating effect was also observed. Bicyclic and tricyclic analogues react similarly.     

Formation of 1,3-oxathioles and 1,3-oxaselencles by reactions of carbonyl-stabilized sulfonium ylides with elemental sulfur and selenium

Carbonyl-stabilized sulfonium ylides readily react with elemental sulfur and selenium to afford 1,3-oxathiole and 1,3-oxaselenole derivatives, respectively, in good yields, thus providing a simple method for constructing these ring systems which uses easily accessible compounds as starting materials.     

Nucleophilic substitution by grignard reagents on sulfur mustards

With proper activation of the leaving group, sulfur mustards react with Grignard reagents with neighboring group participation of the sulfur atom. 2,6-Dichloro-9-thiabicyclo[3.3.1]nonane is especially useful in this regard, providing clean reactivity with organomagnesium nucleophiles on a topologically constrained scaffold.     

Synthesis and antibacterial activity of hydroxylated 2-arylbenzothiazole derivatives

Abstract

N-acyliminium reagents formed in situ from benzothiazole and alkyl chloroformates react with hydroxyarenes in a Friedel-Crafts manner, providing access to 2-(hydroxyaryl)-benzothiazolines with antibacterial properties.     

A convergent route to functional protected amines,diamines, and β-amino acids

Phthalimide protected amines react with NBS under peroxide initiation to give geminal phthalimido-bromo derivatives, which are readily converted into the corresponding xanthates. These xanthates in turn undergo radical additions to numerous olefins, providing a convergent and modular access to densely functionalized protected amines and diamines.     

Metal- and chemical-oxidant-free C-H/C-H cross-coupling of aromatic compounds: the use of radical-cation pools

Pool and couple: A method for oxidative C-H/C-H cross-coupling has been developed using "radical-cation pools". Aromatic compounds react with aryl radical cations, which are generated and accumulated by low-temperature electrolysis (see scheme). This method avoids both the nonselective oxidation of substrates and oxidation of products and effects the C-H/C-H cross-coupling of aromatic compounds without metal complexes and chemical oxidants.     

Catalytic asymmetric domino Michael addition-alkylation reaction: enantioselective synthesis of dihydrofurans

A catalytic enantioselective synthesis of dihydrofurans has been developed. 1,3-Dicarbonyl derivatives react with (E)-β,β-bromonitrostyrenes in the presence of a chiral bifunctional thiourea catalyst providing mild and efficient access to diverse polysubstituted dihydrofurans in good yields and enantioselectivities.     

Reaction of 2,3-Dihalopropionic Acids and Their Derivatives with P- and N-Nucleophiles

3-(Triphenylphosphoniochlorido)acrylic and 2,3-dichloropropionic acids react with triphenylphosphine to form 1,2-bis(triphenylphosphoniochlorido)ethane. Under analogous conditions, 2,3-dibromopropionic acid undergoes debromination followed by triphenylphosphine addition to give, after water treatment, 3-(triphenylphosphoniobromido)propionic acid. 2,3-Dihalopropionitriles react similarly, providing 3-(triphenylphosphoniohalido) propionitriles. The reaction of 2,3-dibromopropionamide with triphenylphosphine was performed to show that E-(triphenylphosphoniobromido)acrylic acid is capable, by contrast to what was reported previously, of reacting with triphenylphosphine. Pyridine forms with 2,3-dihalopropionic acids vinylpyridinium halides, while the reactions with aliphatic amines gives rise to dehydrohalogenation products.     

Stereoselective Wittig olefination reactions employing a novel ortho-P-aryl alkoxide effect

Non-stabilized ortho-P-alkoxy-substituted ylides react with aromatic and aliphatic aldehydes providing (E)-olefins with high stereocontrol, also allowing easy phosphine oxide removal in certain cases.     

Highly diastereroselective synthesis of dihydrofurans and dihydropyrroles via pyridine catalyzed formal [4+1] annulation

A pyridine-catalyzed ylide cyclization affording dihydrofurans and dihydropyrroles has been developed. In the presence of a catalytic amount of pyridine and Fe(Tcpp)Cl, α-ylidene-β-diketones and α,β-unsaturated imines react with diazoacetates providing dihydrofurans and dihydropyrroles respectively, in up to 96% yield with high diastereoselectivities.     

Amination of benzylic C-H bonds by arylazides catalyzed by CoII-porphyrin complexes: a synthetic and mechanistic study

Co(II)-porphyrin complexes catalyze the reaction of aromatic azides (ArN(3)) with hydrocarbons that contain a benzylic group (ArR(1)R(2)CH) to give the corresponding amines (ArR(1)R(2)C-NHAr). When at least one of the R substituents is hydrogen, the catalytic reaction proceeds further to give the imine ArRC=NAr in good yields. The reaction mechanism has been investigated. The reaction proceeds through a reversible coordination of the arylazide to the Co(II)-porphyrin complex. This unstable adduct can either react with the hydrocarbon in the rate-determining step or decompose by a unimolecular mechanism to afford a putative "nitrene" complex, which reacts with more azide, but not with the hydrocarbon, to afford the byproduct diaryldiazene. The kinetics of the catalytic reaction have been investigated for a range of azides and substituted toluenes. Arylazides with electron-withdrawing substituents react at a faster rate and a good correlation is found between the log(k) and the Taft parameters. On the other hand, an excellent correlation between the logarithm of the rate for substituted toluenes relative to that of toluene and a radical parameter (sigma*JJ) alone was found, with no significant contribution by polar parameters. An explanation has been proposed for this anomalous effect and for the very high isotopic effect (k(H)/k(D)=14) found.     

Poly(terephthalic acid anhydride) as a latent monomer in polybenzoxazole synthesis

High molecular weight poly(p-phenylenebenzobisoxazole) (PBO) was prepared from poly(terephthalic acid anhydride) (PTAA) and 1,3-diamino-4,6-dihydroxybenzene dihydrogenchloride in polyphosphoric acid (PPA). PTAA may react directly with the o-aminophenol groups to form benzoxazoles or react with PPA to generate terephthalic acid (TA) of very small particle size, which dissolves readily in PPA. PTAA provides the advantages of bypassing the requirement of small particle size TA, reducing the amount of water liberated by half, and possibly providing faster kinetics in PBO synthesis. © 1994 John Wiley & Sons, Inc.     

Porphyrins and their derivatives: XXV. Reaction of 2-formyl-5,10,15,20-tetraphenylporphyrin with diazomethane

2-Formyl-5,10,15,20-tetraphenylporphyrin and its copper and zinc complexes react with diazomethane in a mixture chloroform-alcohol providing the corresponding 2-acetyl-and 2-acetonyl derivatives. In a pure chloroform main product of diazomethane reaction with 2-formyl-5,10,15,20-tetraphenylporphyrin is 2-acetyl-5,10,15,20-tetraphenylcyclopropa[b]chlorin.     

N-tosylcarboxamide as a transformable directing group for Pd-catalyzed C-H ortho-arylation

The N-tosylcarboxamide group offers the possibility of directing the Pd-catalyzed C-H arylation of arenes providing a new entry to biarylcarboxamides. Moreover, its ability to react according to different reaction conditions including intramolecular reactions makes it a pivotal directing group for a divergent synthesis of biaryl-based compounds.     

Observation and mechanistic study of facile C-O bond formation between a well-defined aryl-copper(III) complex and oxygen nucleophiles

A well-defined macrocyclic aryl–Cu(III) complex (2) reacts readily with a variety of oxygen nucleophiles, including carboxylic acids, phenols and alcohols, under mild conditions to form the corresponding aryl esters, biaryl ethers and alkyl aryl ethers. The relationship between these reactions and catalytic C-O coupling methods is demonstrated by the reaction of the macrocyclic aryl–Br species with acetic acid and p-fluorophenol in the presence of 10 mol% Cu(I). An aryl-Cu(III)-Br species 2(Br) was observed as an intermediate in the catalytic reaction. Investigation of the stoichiometric C-O bond-forming reactions revealed nucleophile-dependent changes in the mechanism. The reaction of 2 with carboxylic acids revealed a positive correlation between the log(k(obs)) and the pK(a) of the nucleophile (less-acidic nucleophiles react more rapidly), whereas a negative correlation was observed with most phenols (more-acidic phenols react more rapidly). The latter trend resembles previous observations with nitrogen nucleophiles. With carboxylic acids and acidic phenols, UV-visible spectroscopic data support the formation of a ground-state adduct between 2 and the oxygen nucleophile. Collectively, kinetic and spectroscopic data support a unified mechanism for aryl-O coupling from the Cu(III) complex, consisting of nucleophile coordination to the Cu(III) center, deprotonation of the coordinated nucleophile, and C-O (or C-N) reductive elimination from Cu(III).     

N8-芳基取代4-氨基-6-氯-7(8H)-蝶啶酮的合成

通过N4-芳基取代4,5,6-三氨基嘧啶与草酸二水合物环合, 得到N8-芳基取代4-氨基-5,8二氢-6,7-蝶啶二酮, 再经氯代, 得到新型N8-芳基取代4-氨基-6-氯-7(8H)-蝶啶酮, 用红外光谱、核磁共振氢谱、核磁共振碳谱、质谱和元素分析确证了其结构. 用X-ray单晶衍射测定了4-氨基-6-氯-8-对甲苯基-7(8H)-蝶啶酮(3a)的晶体结构, 证明了环合反应的区域选择性.