Complementary Iron(II)‐Catalyzed Oxidative Transformations of Allenes with Different Oxidants. Issue 3 (4th December 2015)

• Record Type: Journal Article
• Authors: Sabbasani, Venkata R.; Lee, Hyunjin; Xia, Yuanzhi; Lee, Daesung
• Is Part Of: Angewandte Chemie international edition. Volume 55:Issue 3(2016)
• Page Start: 1151
• Page End: 1155
• Publication Date: 2015-12-04
• Subjects: allenes -- density-functional calculations -- iron -- oxidation -- synthetic methods; Chemistry -- Periodicals; 540
• DOI: 10.1002/anie.201510006
• Languages: English
• ISSNs: 1433-7851

Abstract

Abstract: Substituent‐ and oxidant‐dependent transformations of allenes are described. Given the profound influence of the substituent on the reactivity of allenes, the subtle differences in allene structures are manifested in the formation of diverse products when reacted with different electrophiles/oxidants. In general, reactions of nonsilylated allenes involve an allylic cation intermediate by forming a C−O bond, at the sp‐hybridized C2, with either DDQ (2, 3‐dichloro‐5, 6‐dicyano‐ p ‐benzoquinone) or TBHP ( tert ‐butyl hydroperoxide), along with FeCl2 ⋅4 H2 O (10 mol %). In contrast, silylated allenes favor the formation of propargylic cation intermediates by transferring the allenic hydride to the oxidant, thus generating 1, 3‐enynes (E1 product) or propargylic THBP ethers (SN 1 product). The formation of these different putative cationic intermediates from nonsilylated and silylated allenes is strongly supported by DFT calculations. Abstract : Profound impact : Iron(II)‐catalyzed transformations of allenes induced by either DDQ or t BuOOH depend on the substituent on the allenes. Nonsilylated and silylated allenes show complementary reactivity upon exposure to DDQ and t BuOOH in the presence of an iron(II) catalyst. Nonsilylated allenes incorporate the oxidant at the sp‐hybridized carbon, whereas the silylated allenes generate 1, 4‐dehydrogenated 1, 3‐enynes. DDQ=2, 3‐dichloro‐5, 6‐dicyano‐1, 4‐benzoquinone.