There has been much speculation that enzymes change the nature of the transition state for phosphoryl transfer from the dissociative transition state observed in solution reactions to an associative transition state at the enzyme's active site. This proposal can be tested by comparing linear free energy relationships (LFERs) for nonenzymatic and enzymatic reactions, provided that the specificit...

The presence of substituents at designated sites about the chlorin macrocycle can alter the spectral properties, a phenomenon that can be probed through synthesis. Prior syntheses have provided access to chlorins bearing distinct aryl substituents (individually or collectively) at the 5, 10, and 15-positions, but not the 20-position. A new Western half (5-phenyl-2,3,4,5-tetrahydro-1,3,3-trimeth...

Important aspects of the electrochemical reduction of aryl thiocyanates were investigated. A striking change in the reductive cleavage mechanism as a function of the substituent on the aryl ring of the aryl thiocyanate is observed. A similar behavior has been reported for benzyl halides. This is different from what is widely reported for aryl halides where a stepwise mechanism is taking place r...

A new one-pot approach for the synthesis of aryl a-keto ester based on the diazo transfer and oxidation of diazo group is developed. 2005 Elsevier Ltd. All rights reserved. 1 3 Ar OMe O [O] Ar OMe O O Ar OMe N2 [O] Base ArSO2N3 a-Keto acids and esters have been important compounds as natural products and as the building blocks in organic synthesis. Over the past decades, various methods have be...

Total syntheses of yatakemycin, PDE-II, dictyodendrins, and heptaphylline are described. This article focuses on the formation of aryl carbon-nitrogen bonds by two methods: first by an aromatic amination reaction using a combination of CuI and CsOAc, and then by a benzyne-mediated one-pot cyclization-functionalization sequence. The aryl amination reaction shows a high functional group compatibi...

Reactions of the aryl complexes Rh(aryl){? 3 -P,O,P-[xant(P i Pr 2 ) ]} (1; = 3,5-Me C 6 H (a), 5 (b), 3,5-Cl (c), 3-FC 4 (d); xant(P 9,9-dimethyl-4,5-bis-(diisopropylphosphino)xanthene) with O , CO, and MeO CC?CCO Me have been performed. Under 1 atm pentane solutions afford dinuclear peroxide derivatives [Rh(aryl){? -P,P-xant(P }] (?-O (2a–2d) as yellow solids. In solution, these species are u...

Despite increasing pharmaceutical importance, fluorinated aromatic organic molecules remain difficult to synthesize. Present methods require either harsh reaction conditions or highly specialized reagents, making the preparation of complex fluoroarenes challenging. Thus, the development of general methods for their preparation that overcome the limitations of those techniques currently in use i...

Although biosynthetic gene clusters (BGCs) have been discovered for hundreds of bacterial metabolites, our knowledge of their diversity remains limited. Here, we used a novel algorithm to systematically identify BGCs in the extensive extant microbial sequencing data. Network analysis of the predicted BGCs revealed large gene cluster families, the vast majority uncharacterized. We experimentally...

We report the synthesis of a series of aryl- or alkyl-substituted 2-mercaptobenzothiazoles by direct thiolation of benzothiazoles with aryl or alkyl thiols via copper-mediated aerobic C-H bond activation in the presence of stoichiometric CuI, 2,2'-bipyridine and Na(2)CO(3). We also show that the approach can be extended to thiazole, benzimidazole, and indole substrates. In addition, we present ...

A mild, efficient synthesis of sulfonyl fluorides from aryl and heteroaryl bromides utilizing palladium catalysis is described. The process involves the initial palladium-catalyzed sulfonylation of aryl bromides using DABSO as an SO2 source, followed by in situ treatment of the resultant sulfinate with the electrophilic fluorine source NFSI. This sequence represents the first general method for...