Tandem Horner-Wadsworth-Emmons Olefination/Claisen Rearrangement/Hydrolysis Sequence: Remarkable Acceleration in Water with Microwave Irradiation

Abstract

T a n d e m H o r n e r -Wa d s w o r t h -E m m o n s O l e f i n a t i o n / C l a i s e n R e a r r a n g e m e n t

Microwave-Assisted Synthesis in Water as Solvent

“…A tandem three-step, one-pot protocol involving Horner-Wadsworth-Emmons (HWE) olefination, Claisen rearrange-ment, and a hydrolysis sequence in the synthesis of R-keto acids 133 was developed by Quesada and Taylor. 142 Aldehydes are reacted with allyl phosphonate 132 in aqueous K 2 CO 3 at 105 °C for 10 min to furnish the products 133 in good to excellent yields (Scheme 71). Interestingly, the outcome of the tandem process could be tuned by the temperature.…”

Claisen Rearrangement of Aliphatic Allyl Vinyl Ethers from 1912 to 2012: 100 Years of Electrophilic Catalysis

“…Detailed reports on the synthetic access to acyclic 2-alkoxycarbonyl-substituted allyl vinyl ethers have appeared recently. For the genesis of the critical vinyl ether double bond, they rely on an aldol condensation approach, 72 the Horner-Wadsworth-Emmons olefination, 73 or the O-allylation of α-keto ester enolates. 74 Each method has its ad-vantages and disadvantages, particularly with respect to structural diversity and control of the vinyl ether double bond configuration.…”

Microwave-Assisted Claisen and Aza-Claisen Rearrangements

“…The optimized sequence is carried out in water with microwave irradiation and involves sequential Horner-Wadsworth-Emmons olefination, CR and ester hydrolysis [57]. The optimized sequence is carried out in water with microwave irradiation and involves sequential Horner-Wadsworth-Emmons olefination, CR and ester hydrolysis [57].…”