Total Synthesis of Spirobacillene A Unsworth, William P; Cuthbertson, James D; Taylor, Richard J. K
Organic letters,
07/2013, Letnik:
15, Številka:
13
Journal Article
Recenzirano
The first total synthesis of spirobacillene A, an indole alkaloid isolated from Lysinibacillus fusiformis, is reported. A Lewis acid mediated spirocyclization of an anisole derivative onto a tethered ...ynone was used as a key step, drawing inspiration from a potential biosynthesis of the natural product.
A novel copper(II)-mediated route for the conversion of anilides into 3,3-disubstituted-oxindoles is described which proceeds via a formal C-H, Ar-H coupling process.
Indole-ynones have been established as general substrates for radical dearomatizing spirocyclization cascade reactions. Five distinct and varied synthetic protocols have been ...developedcyanomethylation, sulfonylation, trifluoromethylation, stannylation and borylationusing a variety of radical generation modes, ranging from photoredox catalysis to traditional AIBN methods. The simple and easily prepared indole-ynones can be used to rapidly generate diverse, densely functionalized spirocycles and have the potential to become routinely used to explore radical reactivity. Experimental and computational investigations support the proposed radical cascade mechanism and suggest that other new methods are now primed for development.
“One-pot” processes in which alcohol oxidations are combined with further elaboration of the carbonyl intermediate are reviewed. Sequential processes are briefly discussed, but most attention is ...centered on tandem processes; that is, oxidations carried out in the presence of a nucleophilic trapping agent, rather than those in which the trapping agent is added after the oxidation is complete. As part of this Account, a comprehensive review of the discovery of tandem oxidation processes (TOP) will be given together with applications in alkene-forming reactions, cyclopropanations, and imine, oxime, amine, and heterocycle formation.
A double C–H, Ar–H coupling process for the conversion of bis-anilides into spirocyclic bis-oxindoles, enabling the concomitant formation of two all-carbon quaternary centers at oxindole 3-positions ...in a diastereoselective manner, is described. The optimum cyclization conditions utilize stoichiometric Cu(OAc)2·H2O/KOtBu in DMF at 110 °C and have been applied to prepare a range of structurally diverse bis-spirooxindoles in fair to good yields (28–77%); the method has also been extended to prepare bis-oxindoles linked by a functionalized acyclic carbon chain.
trans-PdBr(N-Succ)(PPh3)2 (1) is a universally effective precatalyst for Suzuki−Miyaura cross-couplings of benzylic halides with aryl- or heteroarylboronic acids. Substituted aryl halides and ...halogenated cyclic enones can be cross-coupled with aryl- or vinylboronic acids in excellent yields. Catalyst recycling is also demonstrated.
A series of high-yielding silver(I)-catalyzed cyclization reactions of pyridine-, isoquinoline-, and pyrazine-ynones are described. The operationally simple and mild reaction conditions are a ...significant improvement over previously reported thermal cyclizations. The quinolizinone products were also used in a novel dearomatization strategy to prepare 0.53 g of the alkaloid lasubine II in five steps and 36% overall yield.
A new low-temperature procedure for the synthesis of 3,3-disubstituted 2-oxindoles via cross-dehydrogenative coupling (CDC) is reported. The use of a strong, nonreversible base in these reactions has ...been found to effect a dramatic drop in reaction temperature (to room temperature) relative to the current state-of-the-art (>100 °C) procedure. When employing iodine as an “oxidant”, new evidence suggests that this transformation may occur via a transiently stable iodinated intermediate rather than by direct single-electron oxidation.
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