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Abstract A Diels–Alder reaction‐based strategy for the synthesis of indoles and related heterocycles is reported. An intramolecular cycloaddition of alkyne‐tethered 3‐aminopyrones gives 4‐substituted indolines in good yield and with complete regioselectivity. Additional substitution is readily tolerated in the transformation, allowing synthesis of complex and non‐canonical substitution patterns. Oxidative conditions give the corresponding indoles. The strategy also allows the synthesis of carbazoles. The method was showcased in a formal synthesis of lysergic acid.
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Development of an Allenyne‐Alkyne [4+2] Cycloaddition and its Application to Total Synthesis of Selaginpulvilin A
Abstract A new [4+2] cycloaddition of allenyne‐alkyne is developed. The reaction is believed to proceed with forming an α,3‐dehydrotoluene intermediate. This species behaves as a σπ‐diradical to react with a hydrogen atom donor, whereas it displays a zwitterionic reactivity toward weak nucleophiles. The efficiency of trapping α,3‐dehydrotoluene depends not only on its substituents but also the trapping agents. Notable features of the reaction are the activating role of the extra alkyne of the 1,3‐diyne that reacts with the allenyne moiety and the opposite mode of trapping with oxygen and nitrogen nucleophiles. Oxygen nucleophiles result in the oxygen‐end incorporation at the benzylic position of the α,3‐dehydrotoluene, whereas with amine nucleophiles the nitrogen‐end is incorporated into the aromatic core. Relying on the allenyne‐alkyne cycloaddition as an enabling strategy, a concise total synthesis of phosphodiesterase‐4 inhibitory selaginpulvilin A is realized.
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- Award ID(s):
- 2055055
- PAR ID:
- 10372913
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Chemistry – A European Journal
- Volume:
- 28
- Issue:
- 56
- ISSN:
- 0947-6539
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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