Transition metal-catalyzed reactions
Jin-Quan Yu of Cambridge University reports (Org. Lett. 2003, 5, 4665. ) that Pd nanoparticles catalyze the hydrogenolysis of benzylic epoxides. The reaction proceeds with inversion of absolute configuration (1 -> 2).
Laurel Schafer of the University of British Columbia reports (Org. Lett. 2003, 5, 4733. ) that terminal alkynes undergo smooth hydroamination with a Ti catalyst. The intermediate imine 4 can be hydrolyzed to the aldehyde 5 or reduced directly to the amine 6. The alkyne to aldehyde conversion has previously been carried out by hydroboration/oxidation (J. Org. Chem. 1996, 61, 3224. ), hydrosilylation/oxidation (Tetrahedron Lett. 1984, 25, 321. ), or Ru catalysis (J. Am. Chem. Soc. 2001, 123, 11917. ). There was no previous general procedure for the anti-Markownikov conversion of a terminal alkyne to the amine.
The construction of enantiomerically-pure carbocycles is a general problem in organic synthesis. Dirk Trauner (UC Berkeley) reports (Org. Lett. 2003, 5, 4113. ) an elegant intramolecular Heck cyclization. The alcohol 7 is readily prepared in enantiomerically-pure form. Conditions can be varied so that either 8 or 9 is the dominant product from the cyclization.