RCM approach toward 1,6-methano[12] - and [14]annulenes and their bisdehydro-derivatives

ORGN 518

Yor-Yu Chen, ych0041@hunter.cuny.edu1, Shu-Ya Hsu1, Ronnie Benshafrut, ronnie.benshafrut@weizmann.ac.il2, Louis J. Todaro3, and Klaus G. Grohmann, gklaus@hunter.cuny.edu3. (1) Department of Chemistry, Hunter College, Graduate School of the City University of New York, 695 Park Ave, New York, NY 10021, (2) AMOS, Ltd, Weizmann Institute of Science, Rehovot, 76100, Israel, (3) Department of Chemistry, Hunter College, Graduate School of the City University of New York, 695 Park Avenue, New York, NY 10021
A new general synthesis for 3,4-Benzo-1,6-methano[12]annulene 1 and 3,4-benzo-1,6-methano[14]annulene 2 based on the ring closing olefin metathesis (RCM) has been developed in our group. Dialdehyde 4 upon reaction with excess allyl- or 3-butenyl-magnesdium bromide gave two pairs of epimeric diols, which after esterification with acetic anhydride underwent smooth RCM. The cyclized diacetates could be converted into annulenes 1 and 2. Compound 1 displays a reduced paratropicity compared with the non-benzannelated system. The X-ray structure of 1 at 100K surprisingly showed a relatively planar system with the C9-C10 double bond syn to the CH2 bridge. The bridged [14]annulene 2 is rather flexible at room temperature. Its low temperature 1H-NMR spectrum clearly indicates diatropic behaviour. A comparison between 1 and 2 as well as progress toward the synthesis and characterization of the 7,8,13,14-Bisdehydro-1,6-methano[14]annulene 3 will be presented.

 

Physical Organic Chemistry, Metal-Mediated Reactions, Asymmetric Reactions and Syntheses
8:00 PM-10:00 PM, Tuesday, August 21, 2007 BCEC -- Exhibit Hall - B2, Poster

Division of Organic Chemistry

The 234th ACS National Meeting, Boston, MA, August 19-23, 2007