In conclusion, we have successfully achieved the first visible light-

induced, Pd-catalyzed asymmetric [5+2] cycloaddition of VECs with α-

diazoketones. This methodology provides an enantioselective approach for

accessing a variety of 7-membered lactones bearing chiral quaternary

stereocenters. Preliminary mechanistic studies suggested that the binding of

two phosphoramidite ligands to the palladium center was responsible for

the high reaction efficiency and enantioselectivity. The transformation

described in this work represents a significant expansion of ketene

chemistry into the construction of challenging medium-sized rings.

Enantioselective Trapping of Pd-Containing 1,5-Dipoles by Photo-generated Ketenes: Access to 7-Membered Lactones Bearing Chiral Quaternary Stereocenters

Yi Wei, Song Liu, Miao-Miao Li, Yi Li, Yu Lan, Liang-Qiu Lu,* and Wen-Jing Xiao*

Wei, Y.; Liu, S.; Li, M.-M.; Li, Y.; Lan, Y.; Lu, L.-Q.;* Xiao, W.-J. * J. Am. Chem.

Soc., 2019, 141, 133–137.

AcknowledgmentWe are grateful to the National Science Foundation of China (No. 21822103, 21820102003, and 21472057), the Program of

Introducing Talents of Discipline to Universities of China (111 Program, B17019) for support of this research.

College of Chemistry, Central China Normal University, 152 Luoyu Road, Wuhan, Hubei, China, 430079

Conclusion 7

References 8

Proposed Stereoinduction Modes6

Introduction 1

Reaxys PhD Prize Symposium 2019, October 3-4, Amsterdam, Netherlands.

Reaction Design2

Construction of medium-sized rings in an efficient

and selective way is an important and challenging task in

organic synthesis. Among the ongoing efforts towards this

goal, [5+2] cycloadditions using reactive transition metal

(TM)-containing 1,5-dipolar synthons is a promising approach to

7-membered rings possibly due to the ready availability of the precursors.

However, the successful asymmetric variants have been largely limited to

intramolecular Ru- or Rh-catalyzed processes using chiral feedstocks. To

make TM-catalyzed dipolar cycloadditions more powerful and general in

the synthesis of medium-sized rings, new strategies for achieving these

transformation in high efficiency and selectivity and under mild reaction

conditions are required.

Nonlinear Experiments.4

ESI-MS Analysis of the Pd Complexes5

Selected Results3