Highly chemo- and regioselective rearrangement of α,β-epoxy ketones to 1,3-dicarbonyl compounds in 5 mol dm−3 lithium perchlorate–diethyl ether medium

Room-Temperature Coupling/Decarboxylation Reaction of α-Oxocarboxylates with α-Bromoketones: Solvent-Controlled Regioselectivity for 1,2- and 1,3-Diketones

“…1,2-Diketone and its regioisomer 3-oxo aldehyde can be obtained by the rearrangement of α,β-epoxy ketones under different conditions through either acyl or hydride migrations, respectively . The acyl migration is generally more favored and may be promoted by Lewis acids, protonic acids, and zeolites to afford 3-oxo aldehydes. On the other hand, the hydride migration is less favored and in the presence of Mg­(ClO 4 ) 2 , silica gel, or catalzyed by Fe­(tpp)­OTf (tpp = tetraphenylporphyrin) and TpRu­(PPh 3 ) (MeCN) 2 PF 6 (Tp = tris­(1-pyrazolyl)­borate) generates 1,2-diketones.…”

Intramolecular Involvement of an Oxygen-containing Nucleophilic Group in Epoxy Ring Opening

“…In [20,21] a mechanism was outlined of epoxycarbonyl compounds transformations catalyzed by metal cations. The a,b-epoxyketones were shown to undergo a rearrangement into 1,3-dicarbonyl compounds characterized by high stereo-and regiospecificity in the presence of Lewis acids like LiClO 4 (where the Li + cation played the role of the acid) or InCl 3 .…”

Highly Selective Synthetic Transformations Catalyzed by Lithium Perchlorate in Organic Media

“…Rearrangement of α,β-epoxy ketones in LPDE pounds in 5  LPDE (Scheme 12, reactions 17Ϫ22). [36] The epoxide ring opening/rearrangement reaction in LPDE could proceed by the coordination of the lithium ion to the epoxide oxygen, resulting in the weakening of the epoxide CϪO bond, followed by the regioselective ring opening of the epoxide to give the most stable carbenium ion. [36] This explains why only benzylic and tertiary epoxides undergo rearrangement, because only then can a stable tertiary or benzylic carbenium ion be formed.…”