A Metal-Free Approach for the Synthesis of 2-Tetralones via Carbanion-Induced Ring Transformation of 2H-Pyran-2-ones

Abstract

A metal-free, ultrasound-assisted approach for the synthesis of highly functionalized 2-tetralones in high yields is described. The process involves ring transformation of 2H-pyran-2-ones with the spirocyclic ketone 1,4-cyclohexandione monoethylene ketal to yield spiro­cyclic ketals and subsequent acid-mediated hydrolysis. This protocol is free from any organometallic reagents, is economical and tolerates a wide range of functional groups.

Synthesis of fluorescent aromatic species via ring transformation of α-pyranones and their application in OLEDs, chemosensors, and cell imaging

“…43 Ketene dithioacetals 4 were conveniently synthesized from ethyl cyanoacetate, carbon disulphide and methyl iodide or dimethyl sulfoxide in the presence of a base. 44 Under basic conditions, 4 was further treated with aromatic ketones 5 containing α-Hs to afford 6-aryl-3-cyano-4-methylthio-2 H -pyran-2-ones 6 . 44 Here, enolate of 5 attacks 4 in a Michael addition manner to form intermediate A , which undergoes intramolecular cyclization to form intermediate C , which then eliminates ethanol to furnish 6 .…”

“…44 Under basic conditions, 4 was further treated with aromatic ketones 5 containing α-Hs to afford 6-aryl-3-cyano-4-methylthio-2 H -pyran-2-ones 6 . 44 Here, enolate of 5 attacks 4 in a Michael addition manner to form intermediate A , which undergoes intramolecular cyclization to form intermediate C , which then eliminates ethanol to furnish 6 . 44 Furthermore, 6 was refluxed with N , N -dialkylamines 7 in methanol to afford 4-amino-6-aryl-3-cyano-2 H -pyran-2-ones 8 .…”

“…44 Here, enolate of 5 attacks 4 in a Michael addition manner to form intermediate A , which undergoes intramolecular cyclization to form intermediate C , which then eliminates ethanol to furnish 6 . 44 Furthermore, 6 was refluxed with N , N -dialkylamines 7 in methanol to afford 4-amino-6-aryl-3-cyano-2 H -pyran-2-ones 8 . 44…”

“…44 Furthermore, 6 was refluxed with N , N -dialkylamines 7 in methanol to afford 4-amino-6-aryl-3-cyano-2 H -pyran-2-ones 8 . 44…”

Transition-metal-free synthesis and photophysical studies of highly functionalized (E)-stilbenes

“…The well-known methods to synthesize stilbene derivatives include transition metal couplings, such as Sonogashira, Mizoroki-Heck, Negishi, Suzuki-Miyaura, Stille, Grubbs & McMurry, Knoevenagel-Doebner, Wittig, or Horner-Wadsworth-Emmons (HWE) olefination, Ramberg-Bucklund reactions, and Perkin aldol condensation. [36][37][38] In the course of our continuous investigation into substituted aromatic systems involving donors and acceptors, [39][40][41][42][43][44][45][46] we have devised an efficient approach to craft donor-acceptor p-conjugated (D-p-A) stilbenes. In this molecule, the secondary amine at the C4 position acts as the donor group and the CN group acts as the acceptor functionality.…”