A novel fragmentation reaction of α,β-epoxyketones the synthesis of acetylenic ketones

C‐C‐Fragmentierung: Herkunft und jüngste Anwendungen

“…Eschenmoser berichtete 1967 über eine α,β‐Epoxyketon‐Fragmentierung bekannt, die cyclische Alkine ergab ( 38 → 39 ) 42. 43 Kurz nach dem Erscheinen von Eschenmosers erster Veröffentlichung zu dieser Transformation beschrieb Tanabe im Wesentlichen dieselbe Reaktion44 und ließ eine Untersuchung zur Anwendung auf Secosteroide von Testosteron ( 40 ) folgen (Schema ) 45. Um das Problem der Epoxidierung von α,β‐ungesättigten Ketonen zu umgehen, wurde das Keton zunächst als p ‐Toluolsulfonylhydrazon aktiviert ( VIII ) und dann mit m ‐CPBA behandelt, um die Fragmentierung auszulösen.…”

“… Bodendorfs ursprüngliche Alkinsynthese (1963)41 sowie Eschenmosers und Tanabes Synthese eines cyclischen Alkins (1967) 42. 44 …”

“…Fragmentierungen, die zu Alkinen führen, sind ein Gebiet reger Betätigung. In enger Analogie zu den ursprünglichen Untersuchungen von Eschenmoser und Tanabe42, 44 fragmentierte das bicyclische Epoxyketon 160 in erwarteter Weise und in guter Ausbeute zu dem Cyclodecinon 161 (Schema ) 104. Dies war Teil einer Untersuchung, die den Nutzen verschiedener 1,3,5‐Hexatriene veranschaulichte, die mithilfe einer Eintopfsequenz aus Stille‐ und Heck‐Kupplungen hergestellt worden waren.…”

Alkynes From Furans: A General Fragmentation Method Applied to the Synthesis of the Proposed Structure of Aglatomin B

“…[3] Shortly afterward, the venerable Eschenmoser-Tanabe fragmentation was invented to convert a,b-epoxy ketones into either acetylenic ketones or aldehydes via the intermediacyo ft osylhydrazones. [4] Subsequent variations of this classical method utilized reactions of b-halo, [5] b-phenylseleno, [6] or b-tosylhydrazino-a,b-unsaturated ketones [7] with either an alkylithium or NaOMe to access alkynyl functionalities.M ore recently,t he group of Dudley extended the reaction scope to versatile vinylogous acyl triflates wherein av ariety of alkynyl ketones,a lcohols,a nd amides were afforded as products. [8] In ad ifferent approach, the group of Zard described an iron-mediated decarboxylative ring cleavage of isoxazol-5-one,w hich provided an expedient synthesis of alkynes from b-keto-esters.…”

Alkynes From Furans: A General Fragmentation Method Applied to the Synthesis of the Proposed Structure of Aglatomin B

“…[1] Consequently,t he development of efficient and practical methods to synthesize alkynes has attracted considerable attention from the chemistry community.Among various methods for alkyne synthesis, alkyne-forming fragmentations [2] play aunique role since they offer as traightforward means to the structural modification of complex molecules.The history of such reaction manifolds can be traced back to 1963 when Bodendorf reported the first example of an alkyne-forming fragmentation of b-chloroacroleins ( Figure 1a). [4] Subsequent variations of this classical method utilized reactions of b-halo, [5] b-phenylseleno, [6] or b-tosylhydrazino-a,b-unsaturated ketones [7] with either an alkylithium or NaOMe to access alkynyl functionalities.M ore recently,t he group of Dudley extended the reaction scope to versatile vinylogous acyl triflates wherein av ariety of alkynyl ketones,a lcohols,a nd amides were afforded as products. [4] Subsequent variations of this classical method utilized reactions of b-halo, [5] b-phenylseleno, [6] or b-tosylhydrazino-a,b-unsaturated ketones [7] with either an alkylithium or NaOMe to access alkynyl functionalities.M ore recently,t he group of Dudley extended the reaction scope to versatile vinylogous acyl triflates wherein av ariety of alkynyl ketones,a lcohols,a nd amides were afforded as products.…”