Selektive C‐C‐Bindungsspaltung zur stereoselektiven Synthese acyclischer Systeme

Abstract

Chemiker setzen seit jeher auf die Entwicklung kreativer Strategien zum Aufbau von Kohlenstoff‐Kohlenstoff‐ und Kohlenstoff‐Heteroatom‐Bindungen. Innerhalb dieses Aufsatzes wird ein weiterer Ansatz eingeführt, der schwierige Molekülstrukturen durch selektive C‐C‐Bindungsspaltung zugänglich macht. Obwohl C‐C‐Einfachbindungen nur eingeschränkt reaktiv sind, soll gezeigt werden, dass diese Methodik einen regio‐, diastereo‐ und enantioselektiven Zugang zu facettenreichen Produkten bietet. Die Entwicklung solcher Strategien mag in Zukunft einen schwerwiegenden Einfluss auf die Syntheseplanung haben und zu neuen und innovativen Prozessen unter Verwendung einfacher oder komplexer Kohlenwasserstoffe führen.

Lanthanide‐Catalyzed Reversible Alkynyl Exchange by Carbon–Carbon Single‐Bond Cleavage Assisted by a Secondary Amino Group

“…[6,15] Interestingly,m any of the present reactions can be reversed by as imple change in the molar ratio of the reactants.For example,the reaction between 2a and aliphatic alkynes 1c-f is reversible.The same trend was observed in the exchange between two different aryl acetylenes (e.g., 2h vs. 2i). [6,15] Interestingly,m any of the present reactions can be reversed by as imple change in the molar ratio of the reactants.For example,the reaction between 2a and aliphatic alkynes 1c-f is reversible.The same trend was observed in the exchange between two different aryl acetylenes (e.g., 2h vs. 2i).…”

“…[6][7][8] However,nosuch method for the CÀCcleavage of primary and secondary amines has been reported, mainly owing to the more facile b-H elimination pathways available for metal amides [9] and the potential thermodynamic disadvantages.C urrently,s uccessful metalcatalyzed processes are limited to tertiary amines and bcarbon elimination. [6][7][8] However,nosuch method for the CÀCcleavage of primary and secondary amines has been reported, mainly owing to the more facile b-H elimination pathways available for metal amides [9] and the potential thermodynamic disadvantages.C urrently,s uccessful metalcatalyzed processes are limited to tertiary amines and bcarbon elimination.…”

Aza‐Quaternary Scaffolds from Selective Bond Cleavage of Bridgehead‐Substituted 7‐Azabicyclo[2.2.1]heptane: Total Synthesis of (+)‐Cylindricines C–E and (−)‐Lepadiformine A

“…Furthermore, these strategies are also restricted fort he constructiono faparticular type of an aza-quaternaryf ramework. To address this synthetic challenge, we sought to design the precursor 1,w hich can expeditiously establish these scaffolds by selective bond cleavage [4] of its strained bonds. For example, the cyclohexylamine derivatives 2 were envisioned to be obtained through the "a" bond (CÀNb ond) fragmentation [5] of compound 1,w hereas cleavage of the "c" bond [6] will afford the 2,2,5,5-tetrasubstituted pyrrolidine 4 (Scheme 1).…”

Donor–Acceptor Complex Enables Alkoxyl Radical Generation for Metal‐Free C(sp3)–C(sp3) Cleavage and Allylation/Alkenylation

“…[12] Thealkoxyl radical is known for b-fragmentation reactivity to selectively cleave the adjacent C À Cb ond, however its synthetic application for intermolecular C À Cb ond formation is limited to alkoxyl radicals derived from strained cycloalkanols. [12] Thealkoxyl radical is known for b-fragmentation reactivity to selectively cleave the adjacent C À Cb ond, however its synthetic application for intermolecular C À Cb ond formation is limited to alkoxyl radicals derived from strained cycloalkanols.…”