%0 Generic %A Dake, Gregory R. %A Fenster, Michaël D. B. %A Hurley, Paul B. %A Patrick, Brian O. %D 2004 %T Synthesis of Functionalized 1-Azaspirocyclic Cyclopentanones Using Bronsted Acid or N-Bromosuccinimide Promoted Ring Expansions %U https://acs.figshare.com/articles/dataset/Synthesis_of_Functionalized_1_Azaspirocyclic_Cyclopentanones_Using_Bronsted_Acid_or_i_N_i_Bromosuccinimide_Promoted_Ring_Expansions/3327904 %R 10.1021/jo0493572.s004 %2 https://ndownloader.figshare.com/files/5167114 %K bromosuccinimide %K semipinacol ring expansion reactions %K electrophilic bromine source %K Bromosuccinimide Promoted Ring Expansions Azaspirocyclic ring systems %K Bronsted acid %K Functionalized %X Azaspirocyclic ring systems are present in a variety of alkaloids. Functionalized 1-azaspirocyclopentanones (6, 7, 11, 12) can be efficiently constructed through semipinacol ring expansion reactions of 2-(1-hydroxycyclobutyl)-p-toluenesulfonylenamides (4) promoted by either a Bronsted acid ((S)-(+)-10-camphorsulfonic acid or HCl) or N-bromosuccinimide, an electrophilic bromine source. Reactions promoted by N-bromosuccinimide tend to proceed in higher yields (80−95%) and with greater diastereoselectivity (3:1−1:0) compared to those reactions promoted by a Bronsted acid. In addition, N-bromosuccinimide promoted reactions can produce a complementary stereochemical outcome compared to the reactions using Bronsted acid. %I ACS Publications