A General and Robust Method for the Preparation of (E)- and (Z)-Stereodefined Fully Substituted Enol Tosylates: Promising Cross-Coupling Partners
نویسندگان
چکیده
A robust method for preparing (E)and (Z)-stereodefined fully substituted enol tosylates is described. α-Substituted β-keto esters undergo (E)-selective enol tosylations using TsCl–Me2N(CH2)6NMe2 as the reagent (method A, 13 examples; 63–96%) and (Z)-selective enol tosylations using TsCl–TMEDA–LiCl as the reagent (method B, 13 examples; 62–99%). A plausible mechanism for the (E)and (Z)-enol tosylation selectivity is proposed. A 1H NMR monitoring experiment revealed that TsCl coupled with TMEDA formed a simple N-sulfonylammonium intermediate.
منابع مشابه
Divergent Synthetic Access to E‐ and Z‐Stereodefined All‐Carbon‐Substituted Olefin Scaffolds: Application to Parallel Synthesis of (E)‐ and (Z)‐Tamoxifens
A highly substrate-general synthesis of all-carbon-substituted E- and Z-stereodefined olefins is performed. The method comprises two sets of parallel and stereocomplementary preparations of (E)- and (Z)-α,β-unsaturated esters involving two robust and distinctive reactions: 1) stereocomplementary enol tosylations using readily available TsCl/diamine/(LiCl) base reagents, and 2) stereoretentive N...
متن کاملPreparation of substituted enol derivatives from terminal alkynes and their synthetic utility.
Stereodefined enol derivatives of aldehydes are prepared from terminal alkynes. Specifically, terminal alkynes are known to undergo Cp2ZrCl2-catalyzed methylalumination. Here, we show that the resultant vinylalanes can be oxygenated with peroxyzinc species to generate trisubstituted enolates. Electrophilic trapping with carboxylic anydrides or silyl triflates yields trisubstituted enol esters o...
متن کاملConvergent and Stereospecific Synthesis of Complex Skipped Polyenes and Polyunsaturated Fatty Acids
Skipped polyenes (that is, 1,4-dienes and higher homologues) are stereodefined components of a vast array of biologically important natural products, including polyunsaturated fatty acids. Although widespread in nature, these architectures are generally considered to represent significant barriers to efficient chemical synthesis. Partial reduction of skipped poly-ynes provides a pathway to a su...
متن کاملOne-pot, four-component synthesis of fully substituted 1,3,4-oxadiazole derivatives from N-isocyaniminotriphenylphosphorane (Ph3PNNC), a primary amine, a carboxylic acid and cinnamaldehyde
The imine intermediate generated by the addition of primary amine to the cinnamaldehyde is trapped by the N-isocyaniminotriphenylphosphorane (Ph3PNNC) and a carboxylic acid, and leads to the formation of the corresponding iminophosphorane intermediate. The 1,3,4-oxadiazole derivatives are formed via intramolecular aza-Wittig reaction of the iminophosphorane intermediate. The reactions were comp...
متن کاملNickel-catalysed cross-coupling reaction of aryl(trialkyl)silanes with aryl chlorides and tosylates.
Using highly stable, readily accessible, and recyclable 2-(2-hydroxyprop-2-yl)cyclohexyl-substituted arylsilanes activated by a mild carbonate base, nickel-catalysed silicon-based aryl-aryl cross-coupling reaction proceeds for the first time with inexpensive aryl chlorides and tosylates in a highly chemoselective manner.
متن کامل