Search

A zinc-catalyzed diastereoselective propargylation of t-butanesulfinyl imines is presented. The methodology provided both aliphatic and aryl homopropargylic amines in up to 98:2 and 99.8:0.2 dr, respectively. The utility of the homopropargylic amines was demonstrated by the application to the synthesis of a cis-substituted pyrido-indole through a diastereoselective Pictet-Spengler cyclization.

Oxepines are ring expanded analogs of glycals that can be used to prepare septanose carbohydrates. A route to carbohydrate based oxepines that utilizes oxepinones as a key intermediate has been developed. The oxepinone intermediates were prepared via an amine catalyzed cycloisomerization of furanose hemi-ketals. 1,2-Reduction of the oxepinones followed by acetylation provided the novel ring expanded enol ether products. Moderate diastereoselectivity was observed for the reduction based on the starting oxepinone. 1,4-Addition onto the oxepinones was also demonstrated. Overall, the syntheses reported here will allow for ready access to novel ring expanded carbohydrate analogs.

A zinc-catalyzed diastereoselective propargylation of t-butanesulfinyl imines is presented. The methodology provided both aliphatic and aryl homopropargylic amines in up to 98:2 and 99.8:0.2 dr, respectively. The utility of the homopropargylic amines was demonstrated by the application to the synthesis of a cis-substituted pyrido-indole through a diastereoselective Pictet−Spengler cyclization.

The utility of allenyl and propargyl boronates for the propargylation of aldehydes and ketones mediated by zinc is presented. The reaction is catalytic in zinc with allenyl or propargyl borolanes. The propargylation with crystalline and air-stable propargyl diethanolamine boronates was also achieved. A catalytic cycle is proposed, and preliminary mechanistic studies are discussed.

Oxepines are ring expanded analogs of glycals that can be used to prepare septanose carbohydrates. A route to carbohydrate based oxepines that utilizes oxepinones as a key intermediate has been developed. The oxepinone intermediates were prepared via an amine catalyzed cycloisomerization of furanose hemi-ketals. 1,2-Reduction of the oxepinones followed by acetylation provided the novel ring expanded enol ether products. Moderate diastereoselectivity was observed for the reduction based on the starting oxepinone. 1,4-Addition onto the oxepinones was also demonstrated. Overall, the syntheses reported here will allow for ready access to novel ring expanded carbohydrate analogs.

The utility of allenyl and propargyl boronates for the propargylation of aldehydes and ketones mediated by zinc is presented. The reaction is catalytic in zinc with allenyl or propargyl borolanes. The propargylation with crystalline and air-stable propargyl diethanolamine boronates was also achieved. A catalytic cycle is proposed, and preliminary mechanistic studies are discussed.