Mechanism of the reaction of dihalogeno-oxirans with ketones catalysed by some Lewis acids

Abstract

all cases uf rate constant deterniiiiation the concentration of ketone was constant.

Transformation of oxiranes into other oxygen-containing heterocyclic systems

“…[80], which occur chemoselectively with participation of the outer epoxy fragment. Methanolysis of epoxy derivatives 88 and 89 in alkaline medium [81,82] occurs in a similar way, while the reaction with methanol in acid medium is accompanied by demethylation during heterocyclization, as in the methanolysis of compound 91 [83,84] 1,3-Dioxolanes are known transformation products of epoxy compounds, which are formed in the presence of Lewis acids [86,87]. The cyclization is not hampered by steric strains in oxetane structure 90 [80] (Scheme 50).…”

Synthesis of Acetonides from Epoxides Catalyzed by Erbium(III) Triflate

“…Since the 1930s, oxiranes were demonstrated to react with carbonyl compounds to give dioxolanes in low to moderate yields, [3] but only recently has this reaction received increased interest among organic chemists. BF 3 is the most successfully employed catalyst for this reaction, [4] however, SnCl 4 , [3,5] TiCl 4 , [6] TiCl 3 (OTf) and TiO(TFA) 2 , [7] tetracyanoethylene, [8] CuSO 4 , [9] zeolites, [10] CH 3 ReO 3 , [11] K10-montmorillonite, [12] [Cp*Ir (NCMe) 3 ] 2 þ , [13] RuCl 3 , [14] bismuth(III) salts, [15] 2,4,4,6-tetrabromo-2,5-cyclohexadienone, [16] tin(IV) tetraphenylporphyrin perchlorate, [17] K 5 CoW 12 O 40 · 3 H 2 O, [18] and SnCl 2 , [19] have also been used with varying degrees of success pertaining to yield and selectivity. However, many of these catalysts are rather strong Lewis acids and are incompatible with other functional or protecting groups.…”

Stereochemical Course of the Reaction between Thiocarbonyl Compounds and Oxiranes: Reaction withcis- andtrans-2,3-Dimethyloxirane

“…Its mechanism with different catalysts has been carefully studied [4] [5]. The observed inversion of the configuration of one oxirane Catom indicates an S n 2-type mechanism, involving an attack of the oxo compound onto the activated oxirane.…”