A palladium-catalyzed method for the preparation of sulfonamides is described. The process exhibits significant functional group tolerance and allows for the preparation of a number of arylsulfonyl chlorides and sulfonamides under mild conditions.

Stereodefined enol derivatives of aldehydes are prepared from terminal alkynes. Specifically, terminal alkynes are known to undergo Cp 2 ZrCl 2 -catalyzed methylalumination. Here, we show that the resultant vinylalanes can be oxygenated with peroxyzinc species to generate trisubstituted enolates. Electrophilic trapping with carboxylic anydrides or silyl triflates yields trisubstituted enol esters or silanes, respectively. The tandem carbometalation/oxygenation tolerates free and protected alcohols, heterocycles, olefins and nitriles. Likewise, amination can be accomplished using azodicarboxylates. Stereodefined enol esters can undergo asymmetric dihydroxylation to yield optically-active α-hydroxy aldehydes. Reduction with NaBH 4 provides the diols of 1,1-disubstituted olefins in excellent ee. An application of this methodology to the enantioselective synthesis of the insect pheromone frontalin is presented. Finally, α-hydroxy aldehydes are shown to undergo homologation to a terminal alkyne, reductive amination, oxidation and olefination. Preliminary results indicate that tandem carbometalation/amination can be accomplished with azodicarboxylates. In this way, ene-hydrazines are formed in excellent yield.Stereodefined enol derivatives of α-branched aldehydes (4) represent valuable building blocks for organic synthesis, but limited access to them has compromised their utility. They are most often prepared from the corresponding aldehyde, although these approaches generally afford mixtures of olefin stereoisomers. 1 Furthermore, current strategies for obtaining the α-substituted aldehydes themselves are limited in reaction scope and require multiple synthetic operations. 2 An alternative synthesis of trisubstituted enol derivatives might involve tandem carbometalation-oxygenation of terminal alkynes (Scheme 1). In this regard, we previously documented the carbocupration-oxygenation of terminal alkynes, in which a vinyl copper intermediate (2, M = Cu) was oxidized with t BuOOLi. 3 Electrophilic trapping of the resultant E-enolate (3) generated E-enol esters and silanes. However, methyl-substituted products were not accessible by this method because methyl-cupration of alkynes is not efficient. 4 Accordingly, we sought a general method for obtaining methyl-substituted enol esters and ethers (4, R′=Me). As described below, we have accomplished this objective and have begun to explore the asymmetric transformations of stereodefined enol derivatives. The methylalumination-oxygenation reaction tolerates considerable functionality including protected and free alcohols, heterocycles, and olefins. 9 Electrophilic trapping is not limited to benzoylation: enol acetates and TES enol ethers (entries 9-14) were prepared in high yields as well. Furthermore, in every case studied to date, the enol derivative has been isolated as a single regioisomer with a high E-isomer content (all E/Z ratios > 20/1). 10Trisubstituted, stereodefined enol derivatives of this type were previously inaccessible, and their ready availability a...

A new technique to deconvolute complex (1)H NMR spectra of small molecules has been developed that utilizes shape selective pulses to simultaneously decouple multiple protons. A limitation in the assignment of the relative configuration of small molecules is the ability to accurately obtain coupling constants. Other methods such as the E.COSY and the 2D J-resolved are available to obtain complicated coupling constants; the multiple homonuclear decoupling method (MDEC) described is a rapid and simple technique. Three examples of increasing spectral complexity, menthol, cholesteryl acetate and a C(16) fatty acid, demonstrate the utility of the technique. Increasing the experimental utility, the single pulse MDEC experiment can be incorporated in other 1D experiments, such as a 1D-TOCSY to solve specific problems.

Herein, we propose a modular and general strategy to construct orcinol-type depsides based on the photolysis of functionalized benzodioxinones (I). Notably, resorcinylic esters are obtained without competing isocoumarin (II) formation, exemplified by the first total synthesis of gustastatin in 10 steps from commercially available trihydroxybenzoic acid. [Structure: see text]

Total synthesis enabled the assignment of relative and absolute stereochemistry of nigricanoside A, which was reported to show potent cytotoxicity.

A Photochemical Entry to Depsides: Synthesis of Gustastatin. -(GARCIA-FORTANET, J.; DEBERGH, J. R.; DE BRABANDER*, J. K.; Org. Lett. 7 (2005) 4, 685-688; Dep. Biochem., Univ. Tex. Southwest. Med. Cent., Dallas, TX 75390, USA; Eng.) -Steudel 28-206

A method for the preparation of aryl and heteroaryl sulfonamides using 2,4,6-trichlorophenyl chlorosulfate (TCPC) is described. The reaction of 2-pyridylzinc reagents with TCPC resulted in 2,4,6-trichlorophenyl (TCP) pyridine-2-sulfonates, and the parent pyridine-2-sulfonate was shown to react with amines. Less electron-rich aryl- and heteroarylzinc reagents reacted with TCPC to afford sulfonyl chlorides that were converted in situ to sulfonamides.

Aryl‐ and heteroarylzinc reagents react with 2,4,6‐trichlorophenyl chlorosulfate (TCPC) to afford sulfonyl chlorides which are in situ converted to the corresponding sulfonamides by rapid reaction with various amines.