Catalyst control over sixfold stereogenicity

Achieving control over higher-order stereogenicity is a long-standing goal in stereoselective catalysis to deliberately address more than a twofold number of stereoisomers per stereogenic unit. Current methods allow control over 2 " stereoisomers and their configurations are routinely assigned using the descriptors (R) and (S) or related binary codes. In contrast, conformational analysis extends beyond this dualistic treatment of stereoisomerism, which constitutes an unmet challenge for catalyst stereocontrol. Here, we report that sixfold stereogenicity is tractable by stereoselective catalysis. By controlling a configurationally stable stereogenic axis with six large rotational barriers, a catalytic [2 + 2 + 2] cyclotrimerization selectively governs the formation of one of six stereoisomers with up to 0:0:2:98:0:0 stereocontrol. Moreover, the stereoselectivity is redirectable by stereodivergent catalysis, providing four of the six stereoisomers as major stereoisomers. The underpinnings of conformational analysis and stereoselective catalysis are thereby conceptually reunited. Novel molecular architectures featuring distinct chemical topologies and unexplored chemical designs are anticipated from catalyst control over higher-order stereogenicity.