Transition metal-catalyzed reactions

Jin-Quan Yu of Cambridge University reports (Org. Lett. 2003, 5, 4665. DOI: 10.1021/ol0358509) 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. DOI: 10.1021/ol0359214) 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. DOI: 10.1021/jo960386p), hydrosilylation/oxidation (Tetrahedron Lett. 1984, 25, 321. DOI: 10.1016/S0040-4039(00)99873-3), or Ru catalysis (J. Am. Chem. Soc. 2001, 123, 11917. DOI: 10.1021/ja0119292). 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. DOI: 10.1021/ol035559t) 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.