Hiroki Shigehisa

Learn More
A unique Markovnikov hydroalkoxylation of unactivated olefins with a cobalt complex, silane, and N-fluoropyridinium salt is reported. Further optimization of reaction conditions yielded high functional group tolerance and versatility of alcoholic solvent employed, including methanol, i-propanol, and t-butanol. Use of trifluorotoluene as a solvent made the(More)
A mild, general, and functional group tolerant intramolecular hydroalkoxylation and hydroacyloxylation of unactivated olefins using a Co(salen) complex, an N-fluoropyridinium salt, and a disiloxane reagent is described. This reaction was carried out at room temperature and afforded five- and six-membered oxygen heterocyclic compounds, such as cyclic ethers(More)
Functional group tolerance is one of the important requirements for chemical reactions, especially for the synthesis of complex molecules. Herein, we report a mild, general, and functional group tolerant intramolecular hydroamination of unactivated olefins using a Co(salen) complex, an N-fluoropyridinium salt, and a disiloxane reagent. This method, which(More)
Catalytic hydrofluorination of olefins using a cobalt catalyst was developed. The exclusive Markovnikov selectivity, functional group tolerance, and scalability of this reaction make it an attractive protocol for the hydrofluorination of olefins. A preliminary mechanistic experiment showed the involvement of a radical intermediate.
Full details are provided for an improved synthesis of cortistatin A and related structures as well as the underlying logic and evolution of strategy. The highly functionalized cortistatin A-ring embedded with a key heteroadamantane was synthesized by a simple and scalable five-step sequence. A chemoselective, tandem geminal dihalogenation of an unactivated(More)
One stereocenter makes all the difference: The synthesis and biological evaluation of 17-epi-cortistatin A is reported from a common intermediate used to procure natural cortistatin A. The synthesis features a unique stereocontrolled Raney-Ni reduction process that can be employed to reliably produce both alpha- and beta-configured D-ring aryl steroids.(More)
[reaction: see text] A novel synthetic path to proaporphine alkaloids was established by employing aromatic oxidation with a hypervalent iodine reagent, where an unprecedented carbon-carbon bond forming reaction between the para-position of a phenol group and an enamide-carbon took place smoothly to give the desired spiro-cyclohexadienone.
DOI: 10.1002/anie.201210099 A publication by the Trauner group[1] prompted the authors of this Communication to make structural assignments by re-examination of the NMR experiments for synthetic trichodermatide A: NOESY correlations between H10 and OH9, and between H8 and OH10, were observed. Furthermore, the coupling constant (6.8 Hz) derived from the(More)