Carbene-Catalyzed Tandem [1,2]-Phospha-Brook/[1,4]-Phosphate Rearrangement: Access to α-Ketophosphates via Controlled Cross-Acyloin Condensation

Abstract

The first N-heterocyclic carbene (NHC)-organocatalytic tandem [1,2]-phospha-Brook/[1,4]-phosphate rearrangement is reported. Acyl phosphonates, unlike acyl silanes that are well-exploited, make entry as the acyl anion precursors under NHC catalysis. The reactions proceed with absolute chemoselectivity via cross-acyloin condensation between acyl phosphonates and aldehydes giving the products α-ketophosphates in good to excellent yields. The challenging (enolizable) aliphatic-aliphatic substrates coupling also furnished the desired product in a good yield.

Stitching Triazoles to Arenes via a Transition Metal-Free Aryne Diels–Alder/1,3-Prototropic Shift/Dehydrobromination Cascade

“…With our group’s core objective of developing transition metal-free organocatalytic methods, we started by reacting vinyl triazole 1a with benzyne precursor 2a to obtain 1,2,3-triazole-fused 5,6-dihydronaphthalene 3a (Table ). Using 2.0 equiv of benzyne precursor 2a and 4.0 equiv of CsF in CH 3 CN solvent at room temperature, 3a was obtained in 66% yield (entry 1). Next, we explored different reaction conditions to study their effect on yield.…”

Expedition to Phenanthrene Nucleus: A Two‐decade Research on Bench

“…This method involves directed ortho metalation of 3-ethylbenzamide (86) by using standard metalation conditions using s-BuLi and further boronation, pinacol treatment to obtain boronates (87). The boronate under Suzuki-Miyaura cross-coupling conditions affords biarylamides (88), on LDA treatment yields 9-phenanthrols (89). The 9-phenanthrol underwent Pd-catalyzed hydrogenolysis to afford alkyl phenanthrenes (91) via triflate intermediate (90) similar to that of Scheme 40.…”

“…Brook rearrangement is an intramolecular anionic migration of a silyl group in silyl carbinols from carbon to oxygen in the presence of a base. The phosphonate to phosphate rearrangement variation is termed as phospha Brook rearrangement [89] . In 2015, Terada and co‐workers envisioned a bronsted base‐catalyzed (phosphazene base) intramolecular cyclization of biaryls functionalized α‐ketoester and alkynes 131 by utilizing [1,2]‐phospha‐Brook rearrangement for the synthesis of phenanthrene derivatives 132 .…”

A General Method for α-Oxyacylation of Vinyl Ketones Using Koser’s Reagent

“…The key intermediates of Taking our group's core objective of developing metal-free organocatalytic methods using hypervalent iodines and carbenes forward, we were interested to develop a method for the direct acyloxylation of vinyl ketones. 10 We initiated the investigation using electron-deficient aryl-substituted vinyl ketone 1a and DABCO in AcOH as a solvent (Table 1). Subjecting this substrate to a reaction condition similar to one elsewhere 9 (as in Scheme 1b) did not produce the desired product, leaving the starting material unconsumed (entry1).…”

“…Taking our group’s core objective of developing metal-free organocatalytic methods using hypervalent iodines and carbenes forward, we were interested to develop a method for the direct acyloxylation of vinyl ketones . We initiated the investigation using electron-deficient aryl-substituted vinyl ketone 1a and DABCO in AcOH as a solvent (Table ).…”