- Competing Pathways in the Azomethine Ylide Route to Indoloquinones: An Improved Procedure for the Generation of a Transient 4-Oxazoline from the Oxazolium Salt
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Azomethine ylide generation from the oxazolium salt 22 and PhSiH3/CsF affords complex products derived from the initial cycloadduct 23 via three competing pathways. Colorless intermediates 24-27 have been detected, and their oxidation products 10, 28, and 29 have been identified. Nucleophilic activation of the oxazolium salt 22 is reported using the organic-soluble benzyltrimethylammonium cyanide. This variation affords the unstable cycloadduct 32, which undergoes aromatization via a single pathway involving 24 and 27, and DDQ oxidation gives the indoloquinone 10 in an improved 63% yield. Lower yields using PhSiH3/CsF or NaCN activation methods are attributed to the heterogeneous conditions and interception of the azomethine ylide by unreacted oxazolium salt.
- Vedejs, Edwin,Monahan, Sean D.
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- IMIDAZOLES, OXAZOLES AND THIAZOLES WITH PROTEIN KINASE INHIBITING ACTIVITIES
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The present invention provides compounds of formula I: (I) or a pharmaceutically acceptable derivative thereof, wherein R1, R2, A, G, and W are as described in the specification. These compounds are inhibitors of protein kinase, part
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