4229-86-1Relevant articles and documents
Harnessing the Power of the Asymmetric Grignard Synthesis of Tertiary Alcohols: Ligand Development and Improved Scope Exemplified by One-Step Gossonorol Synthesis
Gilheany, Declan G.,Kavanagh, Saranna E.
supporting information, p. 8198 - 8203 (2020/11/18)
A series of N-substituted cyclohexyldiaminophenolic ligands for the asymmetric Grignard synthesis of tertiary alcohols is reported. The 2,5-dimethylpyrrole-decorated ligand led to improved enantioselectivities and broadened the scope of the methodology. As an exemplar, we report an unprecedented highly selective one-step synthesis of gossonorol in 93% ee, also constituting the shortest formal syntheses of natural products boivinianin B and yingzhaosu C.
Highly enantioselective addition of primary alkyl Grignard reagents to carbocyclic and heterocyclic arylketones in the presence of magnesium TADDOLate preparative and mechanistic aspects
Weber, Beat,Seebach, Dieter
, p. 6117 - 6128 (2007/10/02)
In the presence of equimolar amounts of the Mg alkoxide from α,α,α',α'-tetraphenyl-2,2-dimethyl-1,3-dioxolan-4,5-dimethanol (a TADDOL) primary Grignard reagents (Et, Pr, Bu, Oct, 3-butenyl) add to carbo- and heteroaromatic methyl ketones in THF at -100°C to give tertiary alcohols of enantiomeric excesses reaching values above 98%. The scope and limitation of the method are investigated. The reaction, which occurs in a vigorously stirred heterogeneous mixture, give best results in the absence of steric hindrance of the reacting centers; Grignard reagents made from alkyl bromides are superior to those obtained from chlorides; there is a perfect linear relationship between the ee of the TADDOL and of the product 2-phenyl-2-decanol; those tertiary alcohols of which the absolute configuration is known, are formed by nucleophilic attack from the Re face of the keto carbonyl groups. Three tentative mechanistic models for the stereochemical course of the reaction are discussed.
Reactions between Furyl Ketones and Grignard Reagents. II. Steric Effects in the Reactions of 2-Furyl Ketones with Alkylmagnesium Halides
Sjoeholm, Rainer,Woerlund, Krister
, p. 435 - 442 (2007/10/02)
The effect of steric crowding at the carbonyl carbon of some alkyl 2-furyl ketones, 2-Fur-CO-R (R = Et, i-Pr, and t-Bu), on the reaction with alkyl Grignard reagents, R'MgX (R' = Me, i-Pr, and t-Bu), has been studied.The effect of the size of the alkyl group of the Grignard reagent was also considered.When MeMgI reacts with the ketones only 1,2-addition products are formed.Reactions with i-PrMgCl and t-BuMgCl give considerable amounts of 1,4- and 1,6-addition products besides 1,2-addition.The primary conjugate addition products are easily oxidized to alkyl substituted alkyl 2-furyl ketones and 2-(5H)-furanones when exposed to air.Further, the i-Pr reagent gives reaction products formed by reduction of the carbonyl group.An increase in the amount of conjugate addition products is observed when the size of the alkyl group in the substrate or that of the alkyl group of the reagent is increased.Possible reaction mechanism are discussed.
