Abstract
The existence of a seven-membered cyclic core in several natural products and biomolecules vitalized the research on its synthesis. [5+2] cycloaddition has become a promising strategy for the construction of seven-membered ring systems by the formation of carboncarbon bonds in a single step, with strong regioselectivity and stereoselectivity. This review mainly focuses on recent developments in the area of [5+2] cycloaddition since 2019. Total synthesis of natural products involving [5+2] cycloaddition as a key step leading to the heptacyclic core has also been discussed. Synthesis of fused and bridged ring systems via the reactions involving inter and intramolecular [5+2] cycloadditions like oxidopyrylium-mediated [5+2] cycloadditions, [5+2] cycloadditions of vinyl cyclopropanes (VCPs), vinyl phenols, etc. is explained in the review with the latest examples. This review provides a useful guide for researchers exploring this powerful strategy to create more elegant heptacycles in their future research.
Keywords: [5+2] Cycloaddition, vinyl cyclopropanes, heptacycles, oxidopyrylium, vinyl phenols, enantioselectivity, diastereoselectivity.
Graphical Abstract
[http://dx.doi.org/10.1039/D0CS00365D] [PMID: 32869796]
[http://dx.doi.org/10.1002/cctc.202001195]
[http://dx.doi.org/10.1021/cr300087g] [PMID: 23153111]
[http://dx.doi.org/10.1002/adsc.201701379]
[http://dx.doi.org/10.1021/acs.orglett.8b00989] [PMID: 29733604]
[http://dx.doi.org/10.1021/acs.joc.1c00396] [PMID: 34111355]
[http://dx.doi.org/10.1016/j.tet.2018.04.006] [PMID: 30455508]
[http://dx.doi.org/10.1002/chem.200901463] [PMID: 19637169]
[http://dx.doi.org/10.1002/ejoc.202000914]
[http://dx.doi.org/10.1021/jo201959a] [PMID: 22292462]
[http://dx.doi.org/10.1021/ja4036785] [PMID: 23725341]
[http://dx.doi.org/10.1002/anie.202016895] [PMID: 33471952]
[http://dx.doi.org/10.1021/acs.orglett.9b02498] [PMID: 31512880]
[http://dx.doi.org/10.1039/C8CC09077G] [PMID: 30666326]
[http://dx.doi.org/10.1021/ja993400z]
[http://dx.doi.org/10.1002/adsc.201000695]
[http://dx.doi.org/10.1021/acs.accounts.9b00640] [PMID: 32069021]
[http://dx.doi.org/10.1016/j.tetlet.2021.153588]
[http://dx.doi.org/10.1021/acs.joc.9b01479] [PMID: 31322900]
[http://dx.doi.org/10.1016/j.tetlet.2020.152377]
[http://dx.doi.org/10.1002/adsc.201900271]
[http://dx.doi.org/10.1021/acs.orglett.1c02321] [PMID: 34402626]
[http://dx.doi.org/10.1021/acs.joc.1c00600] [PMID: 34015224]
[http://dx.doi.org/10.1039/C8QO01089G]
[http://dx.doi.org/10.1021/jacs.0c00308] [PMID: 32093468]
[http://dx.doi.org/10.1016/j.tetlet.2020.152324]
(b) Nakamura, H.; Kawakami, M.; Tsukano, C.; Takemoto, Y. Concise construction of the ACDE ring system of calyciphylline A-type alkaloids via [5+2] cycloaddition. Chemistry, 2019, 25(37), 8701-8704.
[http://dx.doi.org/10.1002/chem.201901690] [PMID: 31063603]
[http://dx.doi.org/10.1021/jacs.9b08983] [PMID: 31545036]
[http://dx.doi.org/10.31635/ccschem.021.202000721]
[http://dx.doi.org/10.1055/s-0037-1610790]
[http://dx.doi.org/10.1002/adsc.202000655]
[http://dx.doi.org/10.1002/anie.201811896] [PMID: 30476368]
[http://dx.doi.org/10.1002/anie.202106007] [PMID: 34216095]
[http://dx.doi.org/10.1039/D0OB02159H] [PMID: 33241830]
[http://dx.doi.org/10.1021/acs.orglett.0c02333] [PMID: 32806199]
[http://dx.doi.org/10.1021/acs.orglett.9b04572] [PMID: 31951145]
[http://dx.doi.org/10.1021/jacs.9b07948] [PMID: 31361485]
[http://dx.doi.org/10.1039/C9GC01811E]
[http://dx.doi.org/10.1021/acscatal.0c02956]
[http://dx.doi.org/10.1002/anie.202006366] [PMID: 32618093]
[http://dx.doi.org/10.1021/acs.orglett.6b01194] [PMID: 27199108]
[http://dx.doi.org/10.1039/D0CC05059H] [PMID: 32996972]
[http://dx.doi.org/10.1002/cjoc.202100737]
[http://dx.doi.org/10.1021/acs.orglett.9b04556] [PMID: 31971396]
[http://dx.doi.org/10.1021/acs.orglett.0c02309] [PMID: 32946247]