I. Chromium(III)-catalyzed carbometalation of alkynes. II. Chromium(III)-catalyzed synthesis of allenes via a syn-carbometalation/syn-elimination sequence. III. Palladium(0)-catalyzed synthesis of ene-allenes via cross-coupling reactions with alkenyl trifluoroborates

Abstract

I. Chromium(III)-catalyzed carbometalation of alkynes. Transition metal-catalyzed methods to manipulate unfunctionalized, unsaturated carbon bonds provide access to compounds otherwise difficult to synthesize by standard organic chemistry methods. In this work the generation of substituted alkenes from alkynes in the presence of cationic chromium(III) complexes is explored.* II. Chromium(III)-catalyzed synthesis of allenes. Interest in allenes as biologically active compounds and as chiral transfer reagents has driven the development of general methods for their synthesis. Many syntheses of allenes have been reported; however, few are able to achieve their synthesis with high functional group tolerance and in high enantiomeric excess. Efforts to expand the current methods for the synthesis of allenes are presented herein. Specifically, the syn-carbometalation/ syn-elimination of propargylic substrates via chromium(III) catalysis to produce allenes is reported.* III. Palladium(0)-catalyzed cross-coupling reaction to synthesize ene-allenes. A second method to synthesize allenes is presented. In particular, ene-allenes possessing various functional groups are synthesized in good yields from propargylic carbonates through a Suzuki Miyaura cross-coupling reaction. Additionally, chiral non-racemic ene-allenes are produced with moderate to high enantiomeric excess from propargylic phosphates.* *Please refer to dissertation for diagrams