Cycloaddition reactions with allenamides

Allenes are an important functional group in organic synthesis. Allenamines, a heteroatom substituted subgroup of allenes, have shown potential in the literature, but reports have remained limited due to its high reactivity. Allenamides, a new class of electron-deficient allenamines in which a chiral imidazolidinone or oxazolidinone group is attached off the nitrogen, have been developed and have proven to be a viable functional group. An efficient protocol was developed for the rapid and efficient synthesis of allenamides. After entry, functionalization at the alpha-position was successfully pursued with an application towards an intermolecular Pauson-Khand type cycloaddition.; Cycloaddition chemistry was further examined with chiral allenamides. After an epoxidation of the allenamide, a highly stereoselective [4+3] intermolecular cyclization proceeded to form complex cycloheptanone type structures. An inverse-electron demand Diels-Alder reaction with oxygen containing dienes was experimented with to give highly functionalized pyranyl heterocycles in high yields and diastereoselectivity. These pyranyl heterocycles were manipulated in a variety of short synthesis of C-glycosides featuring a completely unique removal of an anomeric nitrogen containing chiral auxiliary. Similarly, an inverse-electron demand Diels-Alder reaction with 1-azadienes was examined. Diastereoselectivities and yields were found lower, however, they gave highly functionalized aza-cycles which were manipulated in a short synthesis of nitrogen heterocycles featuring a completely novel removal of an anomeric nitrogen-containing chiral auxiliary. Finally, gamma-substituted allenamides were formed in a highly stereoselective manner to provide allenol alcohols, which upon either an acid or a base intramolecular cyclization, provided dihydrofurans. These compounds were shown to undergo highly stereoselective dihydroxylations with the chiral auxiliary shown to control the outcome. Additionally, the chiral auxiliary was removed in what is believed to be the first removal of a nitrogen-containing unit on a five membered ring.; Allenamides were therefore shown to be useful in organic synthesis. Their improved stability, but good reactivity, prove their usefulness as synthetic building blocks. Finally, the products derived from allenamides were shown to be manipulated in a variety of highly stereoselective manners to give viable synthetic intermediates.