Acylation of Hexaphenylbenzene for the Synthesis of [5]Cumulenes. Issue 17 (28th January 2022)

• Record Type: Journal Article
• Authors: Johnson, Matthew A.; Martin, Max M.; Cocq, Kévin; Jux, Norbert; Ferguson, Michael J.; Tykwinski, Rik R.
• Is Part Of: European journal of organic chemistry. Volume 2022:Issue 17(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-01-28
• Subjects: Acylation of Hexaphenylbenzene for the Synthesis of [5]Cumulenes by Rik Tykwinski and co-workers (@TykwinskiGroup, @MaxMJCM) -- Cumulenes -- Friedel-Crafts acylation -- Hexaarylbenzene -- Hexaphenylbenzene -- Isomerization; Chemistry, Organic -- Periodicals; Organic compounds -- Synthesis -- Periodicals; Bioorganic chemistry -- Periodicals; Chemistry, Physical organic -- Periodicals; 547
• DOI: 10.1002/ejoc.202101467
• Languages: English
• ISSNs: 1434-193X

Abstract

Abstract: The Friedel‐Crafts acylation of hexaphenylbenzene is reported, and the reaction favorably provides the monoacylated products 1 a and 1 b . The resulting ketones 1 a and 1 b are used as precursors for the formation of [5]cumulenes, including 6 b in which the sterically demanding HPB moiety affords a diethynyl[5]cumulene that features significant stability (persistence) versus the analog 6 c which lacks the HPB endgroups. The unsymmetrical substitution pattern of the two most soluble derivatives 6 b and 6 c, allows for estimation of rotational barriers for diethynyl[5]cumulenes via VT NMR studies of cis‐trans isomerization. For both molecules, the barrier to rotation is ca. 15 kcal mol −1, which is attenuated in comparison to other [5]cumulenes due to the presence of the ethynyl endgroups. Abstract : Hexaphenylbenzene is appended to [5]cumulenes, a marriage of sp‐ and sp 2 ‐carbon building blocks for synthetic allotropes.