Inter- and Intramolecular Alkyne-Carbonyl Metathesis/1,6-Addition/Oxidative Aromatization Tandem Reactions between 1,6-Diynes and Aldehydes.

We report an efficient synthetic route to 9-arylfluorenes and biaryl compounds from 1,6-diynes and aldehydes via inter- and intramolecular alkyne-carbonyl metathesis/1,6-addition/oxidative aromatization reactions. These tandem reactions are initiated by a BF3·Et2O-promoted tandem inter- and intramolecular alkyne-carbonyl metathesis of 1,6-diynes with carbonyl compounds followed by an In(OTf)3-catalyzed 1,6-addition/oxidative aromatization with iodobenzene diacetate.

Tandem Reaction of Enynyl Acetate: Precursor of Allenyl Ketones.

Deacetylation of enynyl acetates under basic conditions allows convenient access to reactive allenyl ketones, which can then undergo 1,4-addition of nucleophiles to furnish ß,γ-unsaturated ketones. Benzofuran and indole derivatives have also been obtained from enynyl acetates with an o-hetero-atom-substituted aryl group via intramolecular 1,4-addition.

Copper-Catalyzed Tandem Decyclization-Cyclization Reaction of N-Alkynyl-3-hydroxyisoindolin-1-ones Generated from N-Alkynyl Phthalimides: Selective Synthesis of ortho-(2-Oxazolyl)phenyl Ketones.

Selective carbophilic monoaddition on N-alkynyl phthalimides was performed with organometallic reagents to afford 3-substituted N-alkynyl-3-hydroxyisoindolin-1-ones (α-hydroxy ynamides) as a new subgroup of ynamides. Owing to the alkynyl motif on the nitrogen atom, α-hydroxy ynamides were easily isomerized to the corresponding ortho-(2-oxazolyl)phenyl ketones in a CuCl-catalyzed tandem decyclization-cyclization reaction under mild conditions.

Regioselective iodoazidation of alkynes: synthesis of α,α-diazidoketones.

Aryl alkyl alkynes reacted with N-iodosuccinimide (NIS) and trimethylsilyl azide (TMSN3), leading to α,α-diazidoketones via the regioselective addition of IN3 to alkynes. Huisgen cyclization of α,α-diazidoketones generated bis-triazole compounds.

Bi(OTf)3-catalyzed tandem Meyer-Schuster rearrangement and 1,4-addition to the resulting vinyl ketone.

Bi(OTf)3-catalyzed Meyer-Schuster rearrangement of electron-rich propargyl alcohols, followed by 1,4-addition of the resulting vinyl ketone, proceeded smoothly though Meyer-Schuster rearrangement of primary propargyl alcohols is rare. This tandem reaction can be extended to an intramolecular version, featuring a one-pot dihydroquinolone synthesis.

Pyrrolopyrimidine-inhibitors with hydantoin moiety as spacer can explore P4/S4 interaction on plasmin.

In the development of plasmin inhibitors, a novel chemotype, pyrrolopyrimidine scaffold possessing two motifs, a hydantoin-containing P4 moiety and a warhead-containing P1 moiety, is uncovered. A unique feature of the new line of the plasmin inhibitors is that the interaction between the plasmin inhibitors and key subsites in plasmin can be controlled by a spacer like hydantoin. The application of the novel chemotype is demonstrated by 1n and provides further evidence on the importance of hydantoin as the spacer.

Ag- and Au-catalyzed addition of alcohols to ynimides: ß-regioselective carbonylation and production of oxazoles.

Metal-catalyzed reactions of ynimides with alcohols to afford ß-ketoimides and oxazoles are demonstrated. The triple bond of ynamides is generally activated by mineral acids or metal salts to lead to the regioselective addition of nucleophiles at the α-C-atom, because of the inherent electronic bias. In contrast, the two neighboring carbonyl groups of ynimides decrease the electron density of the triple bond and the nucleophiles attack the carbonyl C-atom.

Synthesis and evaluation of tripeptidic plasmin inhibitors with nitrile as warhead.

Plasmin is best known as the key molecule in the fibrinolytic system, which is critical for clot lysis and can initiate matrix metalloproteinase (MMP) activation cascade. Along with MMP, plasmin is suggested to be involved in physiological processes that are linked to the risk of carcinoma formation. Plasmin inhibitors could be perceived as a promising new principle in the treatment of diseases triggered by plasmin. On the basis of the peptidic sequence derived from the synthetic plasmin substrate, a series of peptidic plasmin inhibitors possessing nitrile as warhead were prepared and evaluated for their inhibitory activities against plasmin and other serine proteases, plasma kallikrein and urokinase. The most potent peptidic inhibitors with the nitrile warhead exhibit the potency toward plasmin (IC(50) = 7.7-11 µM) and are characterized by their selectivity profile against plasma kallikrein and urokinase. The results and molecular modeling of the peptidic inhibitor complexed with plasmin reveal that the P2 residue makes favorable contacts with the open binding pocket comprising the S2 and S3 subsites of plasmin.

Identification of novel plasmin inhibitors possessing nitrile moiety as warhead.

Lysine-nitrile derivatives having a trisubstituted benzene, which belongs to a new chemical class, were prepared and tested for inhibitory activities against plasmin and the highly homologous plasma kallikrein and urokinase. The use of the novel chemotype in the development of plasmin inhibitors has been demonstrated by derivatives of compound 9.

N-Alkynyl imides (ynimides): synthesis and use as a variant of highly labile ethynamine.

This study describes the first reliable synthesis of N-alkynyl imides (ynimides). This was accomplished with a copper-catalyzed coupling reaction between alkynyl(triaryl)bismuthonium salts and five-membered imides. We also found that it was possible to utilize N-ethynyl phthalimide as a variant of the highly labile ethynamine. 4-Amino-1,2,3-triazole was successfully obtained via the CuAAC reaction of N-ethynyl phthalimide with azide followed by hydrazinolysis of the phthaloyl protecting group.

Iodobenzene-catalyzed alpha-acetoxylation of ketones. in situ generation of hypervalent (diacyloxyiodo)benzenes using m-chloroperbenzoic acid.

Reported here for the first time is the iodobenzene-catalyzed alpha-oxidation of ketones, in which diacyloxy(phenyl)-lambda3-iodanes generated in situ act as real oxidants of ketones and m-chloroperbenzoic acid serves as a terminal oxidant. Oxidation of a ketone with m-chloroperbenzoic acid in acetic acid in the presence of a catalytic amount of iodobenzene, BF3.Et2O, and water at room temperature under argon affords an alpha-acetoxy ketone in good yield. p-Methyl- and p-chloroiodobenzene also serve as efficient catalysts in this direct oxidation. We found that when the reaction was carried out in the absence of a catalytic amount of iodobenzene, Baeyer-Villiger oxidation of a ketone took place. It is noted that use of water and BF3.Et2O is crucial to the success of this alpha-acetoxylation.

Addition to electron deficient olefins of alpha-oxy carbon- centered radicals, generated from cyclic ethers and acetals by the reaction with alkylperoxy- lambda(3)-iodane.

Thermal decomposition of 1-tert-butylperoxy-1,2-benziodoxol-3(1H)-one in cyclic ethers and acetals at 50 degrees C generates alpha-oxy carbon-centered radicals, which undergo an addition reaction with vinyl sulfones and unsaturated esters.

Synthesis of 1-alkynyl(diphenyl)onium salts of group 16 elements via heteroatom transfer reaction of 1-alkynyl(phenyl)-lambda 3-iodanes.

1-Alkynyl(phenyl)-lambda 3-iodanes undergo selective transfer of the alkynyl groups over the phenyl group onto diphenyl chalcogens. Exposure of 1-alkynyl(phenyl)-lambda 3-iodanes to diphenyl chalcogens (S, Se, and Te) in dichloromethane or 1,2-dichloroethane affords 1-alkynyl(diphenyl)sulfonium, -selenonium, and -telluronium salts in high yields.

Mechanistic investigations on the reaction between amines or amides and an alkylperoxy-lambda3-iodane.

A mechanism involving the intermediate formation of an amine radical cation by single-electron transfer is proposed for the oxidation of secondary amines with alkylperoxy-lambda(3)-iodane. On the other hand, the oxidation of acetamides probably proceeds by a radical process, which involves the direct hydrogen abstraction of the methylene group alpha to the nitrogen atom.