A stereocontrolled Stille cross-coupling reaction, involving the use of Pddba, provides a general procedure for the synthesis of unsymmetrical α-linked bisenone systems. The transformation is achieved in the absence of phosphine ligands under conditions that promote the stabilization of "ligandless" palladium catalysis. The extension of these studies illustrates Suzuki-Miyaura reactions of 2-boryl-2-cyclohexen-1-one with iodide and triflate partners for the synthesis of novel electron-deficient 1,3-dienes.

The atropselective iodination of 2-amino-6-arylpyridines catalyzed by chiral disulfonimides (DSIs) is described. Key to the development of this transformation was the use of a chemoinformatically guided workflow for the curation of a structurally diverse training set of DSI catalysts. Utilization of this catalyst training set in the atropselective iodination across a variety 2-aminopyridine substrates allowed for the recommendation of statistically higher-performing DSIs for this reaction. Data Fusion techniques were implemented to successfully predict the performance of catalysts when classical linear regression analysis failed to provide suitable models. This effort identified a privileged class of 3,3′alkynyl-DSI catalysts which were effective in catalyzing the iodination of a variety of 2-amino-6-arylpyridines with high stereoselectivity and generality. Subsequent preparative-scale demonstrations highlighted the utility of this reaction by providing iodinated pyridines >90:10 er and in good chemical yield.

An enantiocontrolled synthesis pathway has been developed to provide formation of tricyclic amine 7, representing the ABC ring system of the complex alkaloid daphnicyclidin A (1). Our efforts describe preparation of the Z-hexahydro-(1H)-azocine 29 and cyclization to construct the novel 4-azabicyclo[5.3.2]dodecane 31. Transannular reductive amination following the deprotection of 31 gave the desired tertiary amine 7.

Cyclic voltammetry and controlled‐potential (bulk) electrolysis have been used to explore the electrochemical reduction of o‐nitrobenzaldehyde (o‐NBA) and 8 other aldehydes and ketones at glassy carbon cathodes in dimethylformamide containing various tetraalkylammonium tetrafluoroborate salts along with a proton donor (4‐chlorophenol). Cyclic voltammograms for reduction of o‐NBA exhibit three cathodic peaks attributable in succession to (a) one‐electron generation of the nitro radical‐anion, (b) three‐electron formation of the hydroxylamine, and (c) two‐electron production of benzisoxazole (anthranil). These findings have been employed to develop efficient controlled‐potential (bulk) electrosyntheses of the following compounds: benzisoxazole, methylbenzo[c]isoxazole, [1,3]dioxolo[4′,5′,4,5]benzo[1,2‐c]isoxazole, naphtho[2,3‐c]isoxazole, 6‐chlorobenzo[c]isoxazole, 6‐methoxybenzo[c]isoxazole, 3‐methyl‐benzo[c]isoxazole, 3‐isopropylbenzo[c]isoxazole, and 3‐phenylbenzo[c]isoxazole. In addition, we have examined the use of a variety of proton donors to optimize the production of the desired product, and we have been able to recover the proton donor at the conclusion of the electrosynthesis. In each case, the synthesized product was separated by means of normal phase chromatography and identified with the aid of NMR spectros‐copy, gas chromatography (GC), and gas chromatography‐mass spectrometry (GC‐MS). Isolated yields of the desired products range from 63 to 92 %. Moreover, our electrosyntheses are catalyst‐free, environmentally green, and rapid (∼30 min).

A novel annelation strategy has been devised for stereoselective synthesis of tetrahydrocarbazoles. The pathway features a regio- and stereocontrolled condensation of indole and its substituted derivatives with electron-deficient 1,3-dienes via a Michael-Mannich reaction sequence. An extension of this method to include cross-conjugated allenes as substrates also results in a Michael-Mannich-Michael cascade, incorporating 2 equiv of indole with increasing product complexity. The formal 4π + 2π cyclization describes a concise route to polycyclic alkaloids of this family.

Facile oxidation of highly substituted 3,5-hexadien-1-ols using 3-iodoxybenzoic acid (IBX) in DMSO has resulted in a one-pot preparation of 2,3,4,6-tetrasubstituted 2H-pyrans.Cycloisomerizations of the 1-oxatriene moiety, produced in the oxidation, spontaneously occur via a disrotatory oxa-electrocyclization. The 2H-pyran products of Table 1 features three differentiated carbonyl substituents. In Celebration of Professor Yasuyuki Kita on His 77th BirthdayThe pyran heterocycle is a common structural motif found within pharmaceuticals, agrichemicals, and biologically active natural products. Several reviews have summarized a variety of techniques for the preparation of substituted pyrans. 1 Methods for the synthesis of tetrahydropyrans have been extensivelyexplored, and we have previously described a general strategy using asymmetric S E ' allylation reactions for enantiocontrolled syntheses of substituted tetrahydropyrans 2,3 Similarly, the formation of dihydropyrans has attracted much attention because these structural motifs also appear within naturally-occurring macrolactones of biological interest. 4 While syntheses of tetrahydropyrans and dihydropyrans are often focused on issues of stereochemistry and efficient strategies for regiocontrolled substitutions, the increased unsaturation of 2H-pyrans results in the characterization of notably less stable species. Successful methods toward substituted derivatives of this reactive family of pyrans are generally limited in scope.In this communication, we report an efficient preparation of 2H-pyrans stemming from 3-iodoxybenzoic acid (IBX) oxidations of highly substituted 3,5-hexadien-1-ols with in situ electrocyclization. The formation of 2H-pyrans via the oxa-electrocyclization reaction has been reported by several investigators in the course of studies for natural product synthesis, 5 and a recent review has compiled key strategies for

Stereoselective reactions are described which lead to functionalization of the dolabellane skeleton. The stereoselectivity is attributed to conformational effects imposed by the eleven-membered ring. An efficient pathway provides for the stereocontrolled synthesis of nonracemic 6(S)-hydroxy-4(E)-dolabellene-3-one 12 and related derivatives.

MONDAL, P. K.; BAWEL, S. A.; NAG, P. P.; Org. Lett. 16 (2014) 7, 1956-1959, http://dx.doi.org/10.1021/ol5005092 ; Dep. Chem., Indiana Univ., Bloomington, IN 47405, USA; Eng.) -Mais 37-216