Part 1: Synthesis of new camphor-based auxiliaries; Part 2: isomerization/cyclization of acetylenic ketones to cyclopentenones

Abstract

Part 1: Synthesis of New Camphor-Based Auxiliaries. The development of new camphor-based auxiliaries for an enantioselective route to cyclopentenones is discussed. Changes to the basic camphor auxiliary that was used in the original methodology were made, resulting in a series of seven new camphor-based chiral auxiliaries. These modifications were made with the hope of producing a new auxiliary capable of increasing the enantiomeric excesses of the cyclopentenone products. Synthetic routes to each auxiliary are provided along with the results of the cyclopentannelation reaction. Part 2: Isomerization I Cyclization of Acetylenic Ketones to Cyclopentenones Allenyl ketones are key intermediates in the formation of cyclopentenones by cyclopentannelation. A new method for the formation of allenyl ketones in situ is discussed. This has become an attractive method especially for the formation of racemic a-methylene cyclopentenones substituted at the exocyclic methylene. A convenient method for the production of the isolable acetylenic ketone precursors from various propargylic ether and morpholino enamide starting materials is discussed. The results of the in situ isomerization of the acetylenic ketones to their corresponding allenyl ketones and cyclopentenones are also accounted.