Contrasteric coupling of allenes and tetrahydroisoquinolines by iron-catalysed allenic C(sp²)–H functionalisation

Abstract

An iron-catalysed C–H functionalisation of simple monosubstituted allenes for the synthesis of 1-tetrahydroisoquinolinyl 1,1-disubstituted allenes is reported.

Modern Organometallic C−H Functionalizations with Earth‐Abundant Iron Catalysts: An Update

“…Later in the same year, Wang and co-workers reported a similar protocol for the iron-catalyzed CÀ H functionalization of monosubstituted allenes for the synthesis of 1-tetrahydroisoquinolinyl 1,1-disubstituted allenes through cross-dehydrogenative coupling (Scheme 24). [64] Here, the N-carbonylmethoxy tetraisoquinoline (43 a) is firstly submitted to trityl tetrafluoroborate in trifluorotoluene for 3 hours to generate the electrophilic iminium coupling partner. Then, the iminium is reacted with allene (27) in the presence of a Cp*-based iron catalyst [Cp*Fe(CO) 2 (thf)] + [BF 4 ] À and 4-chloro-2,6-lutidine as the base.…”

“…Later in the same year, Wang and co‐workers reported a similar protocol for the iron‐catalyzed C−H functionalization of monosubstituted allenes for the synthesis of 1‐tetrahydroisoquinolinyl 1,1‐disubstituted allenes through cross‐dehydrogenative coupling (Scheme 24). [64] …”

Synthetic applications of hydride abstraction reactions by organic oxidants

“…Allenes can also be used as precursors to the nucleophiles in these reactions. 212 Scheme 72 Trityl cation-mediated protecting group manipulations.…”

“…Allenes can also be used as precursors to the nucleophiles in these reactions. 212 Yesilcimen and co-workers employed the trityl cation to form dienophiles in asymmetric inverse electron-demand hetero Diels-Alder reactions from simple ethers. 213 Oxidizing tetrahydrofuran to form dihydrofuran in the presence of enone 356 and catalyst 357 results in the production of adduct 358 in excellent yield and with high stereocontrol.…”

Designed Iron Catalysts for Allylic C−H Functionalization of Propylene and Simple Olefins

“…Electrophilic attack of the resulting η 1 ‐allyliron species with S E 2′ selectivity then affords the product of net α‐C−H functionalization (Scheme 2a). This catalytic mode has been successfully applied to propargylic and allenylic C−H functionalization, and allylic C−H functionalization at electronically activated sites, delivering a diverse range of products containing new C−C bonds [19a,c,e–f] . By contrast, simple unfunctionalized olefins performed with substantially inferior reactivity, even after further optimization of reaction conditions.…”