New approaches to heterocycles and carbocycles /
Abstract (Summary)The electrophilic cyclization of functionally-substituted alkynes is a very promising route to an extraordinary range of medicinally interesting, functionally-substituted heterocycles and carbocycles. For instance, a variety of substituted isocoumarins and [alpha]-pyrones are readily prepared in excellent yields under very mild reaction conditions by the reaction of o-(l-alkynyl)benzoates and (Z)-2-alken-4-ynoates with IC1,I?, PhSeCl,p-O?NC?H?SCl, and HI. This methodology accommodates various alkynyl esters and has been successfully extended to the synthesis of polycyclic aromatic and biaryl compounds. Electrophilic cyclization of o-(l-alkynyl)benzamides with IC1, I?, and NBS, affords a variety of substituted isoindolin-1-ones in good to excellent yields. In a few cases, substituted isoquinolin-1-ones were obtained as the major product instead. This methodology accommodates various alkynyl amides and functional groups, and has been successfully extended to heterocyclic starting materials. This chemistry has been successfully applied to the formal synthesis of a biologically interesting alkaloid cepharanone B. A variety of substituted polycyclic aromatics are readily prepared in good to excellent yields under very mild reaction conditions by the reaction of 2-(1-alkynyl)biphenyls with IC1, I?, NBS, and p-O?NC?H?SCl. This methodology readily accommodates various functional groups and has been successfully extended to systems containing a variety of polycyclic and heterocyclic rings. The coupling of 2-(1-alkynyl)-2-alken-1-ones with nucleophiles, either catalyzed by AuCl? or induced by an electrophile, provides highly substituted furans in good to excellent yields under very mild reaction conditions. Various nucleophiles, including functionalized alcohols, H?O, carboxylic acids, 1,3-diketones and electron-rich arenes, and a range of cyclic and acyclic 2-(1-alkynyl)-2-alken-1-ones readily participate in these cyclizations. Iodine, NIS, and PhSeCl have proven successful as electrophiles in this process. The resulting iodine-containing furans can be readily elaborated to more complex products using known organopalladium chemistry.
School:Iowa State University
School Location:USA - Iowa
Source Type:Master's Thesis
Date of Publication: