Enantioselective Rhodium-Catalyzed Cycloisomerization of 1,6-Allenynes to access 5/6-Fused Bicycle[4.3.0]nonadienes

Transition-metal-catalyzed cycloisomerization of 1,n-allenynes represents a powerful synthetic tool to rapidly assemble complex polycyclic skeletons from simple linear substrates. Nevertheless, there are no reports of the asymmetric version of these reactions. Moreover, most of these reactions proce...

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Published in:Nature communications 2019-02, Vol.10 (1), p.949-949, Article 949
Main Authors: Deng, Xu, Shi, Li-Yang, Lan, Jialing, Guan, Yu-Qing, Zhang, Xiaoyong, Lv, Hui, Chung, Lung Wa, Zhang, Xumu
Format: Article
Language:English
Subjects:
140/131
140/58
639/638/403/934
639/638/549/933
639/638/77/883
Activation
Allene
Bicycles
Catalysis
Chemistry
Deuterium
Enantiomers
Genetic transformation
Humanities and Social Sciences
Hydrogen bonds
Isomerization
Ligands
multidisciplinary
Organic chemistry
Rhodium
Science
Science (multidisciplinary)
Solvents
Substrates
Transition metals
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Summary:Transition-metal-catalyzed cycloisomerization of 1,n-allenynes represents a powerful synthetic tool to rapidly assemble complex polycyclic skeletons from simple linear substrates. Nevertheless, there are no reports of the asymmetric version of these reactions. Moreover, most of these reactions proceed through a 6-endo-dig cyclization pathway, which preferentially delivers the distal product (via 5/5 rhodacyclic intermediate) rather than the proximal one (via 6/5 rhodacyclic intermediate). Herein, we report an enantioselective rhodium(I)-catalyzed cycloisomerization of 1,6-allenynes to provide the proximal product 5/6-fused bicycle[4.3.0]nonadienes in good yields and with excellent enantioselectivities. Remarkably, this chemistry works perfectly for 1,6-allenynes having a cyclic substituent within the allene component, thereby affording synthetically formidable tricyclic products with excellent enantioselectivities. Moreover, extensive DFT calculations suggest an uncommon pathway involving 5- exo - dig cycloisomerization, ring-expansion, rate-determining alkene isomerization involving C sp3 -H activation, C-C activation of the cyclobutene moiety and finally reductive elimination. Deuterium labeling experiments support the rate-determining step involving the C–H bond activation in this transformation. Cycloisomerization of 1,n-allenynes allows to efficiently assembly polycyclic skeletons, however its asymmetric variant remains elusive. Here, the authors report the enantioselective Rh(I)-catalyzed cycloisomerization of 1,6-allenynes and disclose an uncommon 5-exo-dig pathway via DFT calculations.
ISSN:2041-1723
2041-1723
DOI:10.1038/s41467-019-08900-z