Syntheses and Reactions of 2-Alkyl-1,3-cyclopentanediones (2-Alkyl-3-hydroxy-2-cyclopenten-1-ones)

Acid Chlorides as Formal Carbon Dianion Linchpin Reagents in the Aluminum Chloride-Mediated Dieckmann Cyclization of Dicarboxylic Acids

“…Lewis acid-mediated condensation of 24 results in the formation of cyclic anhydride 26 upon release of 25 . The activated enol 25 subsequently cleaves anhydride 26 , which results in the formation of keto acid 27 . Decarboxylation of 27 and subsequent activation with another equivalent of acid chloride provides activated enol 28 , which undergoes Dieckmann cyclization to yield 17 .…”

Aluminum Chloride-Mediated Dieckmann Cyclization for the Synthesis of Cyclic 2-Alkyl-1,3-alkanediones: One-Step Synthesis of the Chiloglottones

“…The most direct approach to 2-alkyl-1,3-alkanedione building blocks reported to date relies on the conversion of dicarboxylic acids with acid chlorides using superstoichiometric Lewis acids as reagents . While this method provided a synthetically appealing route toward the simpler cyclic-1,3-dione congeners, , subsequent efforts aimed at expanding the substrate scope to more complex motifs were hampered by competing Lewis acid-mediated self-condensation of the requisite acid chlorides to give 4-hydroxy-2-pyrones 18 (Figure ). , …”

Synthesis of 7a-Substituted Hajos−Wiechert Ketone Analogues

“…Key to this process is the availability of the 2-substituted dione 3 . Although these substituted diones are very useful synthetic building blocks for steroid and many other cyclopentanoid natural products, their preparation presents some significant challenges and their availability is limited . Therefore, the first problem that needed to be solved in the development of a route to HW-ketone analogues was the establishment of a general route to 2-substituted 1,3-cyclopentadiones.…”

“…These diones are theoretically available by reaction of 1,3-cyclopentadione 3b with electrophiles. However, yields for these additions are generally quite low because the anion from 3b preferentially undergoes O- rather than C-alkylation. , While a solution to this problem for 2-substituted 1,3-cyclohexadiones was recently reported by Ramachary and Kishor in their preparation of analogues of the Wieland−Miescher ketone, there remains no general synthetic approach to 2-substituted 1,3-cyclopentadiones.…”