A [3,3]-sigmatropic process catalysed by acetate. The decarboxylative Claisen rearrangement

Stereoselective Synthesis of (2S,4R)‐4‐Hydroxypipecolic Acid

“…Ethyl ( R )‐4‐Cyano‐3‐[(4‐methoxybenzyl)oxy]butanoate [(–)‐16]: A solution of (–)‐ 5 (1.092 g, 6.96 mmol) in dichloromethane (7.5 mL) was added to a stirred solution of freshly prepared p ‐methoxybenzyl 2,2,2‐trichloroacetimidate29 (3.01 g, 10.65 mmol) in cyclohexane (15 mL) under N 2 . The solution was cooled to –5 °C and BF 3 · Et 2 O (30 μL) was added dropwise.…”

Molecular Rearrangements: Part 1. Pericyclic Reactions

“…In this case, it has been proposed that decarboxylative silatropic retro-ene rearrangement can occur without the need for the acetate catalyst. 11 Bismuth triflate has been shown to be an effective catalyst for the Claisen rearrangement of allyl naphthyl ether derivatives in refluxing acetonitrile, giving exclusively oallylnaphthol derivatives. Vinylic substitution has been found to cause competing [1,3]sigmatropic migration of the allyl group.…”

“…14 Total diastereoselectivity has been found to occur in an Mg(II)-promoted Claisen de rearrangement of some sugar-derived enol ethers. Treatment of 2-substituted 1-chloro-1-isopropoxycarbonyl epoxides (7) with MgI 2 -Mg followed by allyl bromide-HMPA was found to generate a mixture of allyl enol ethers (9), α-keto esters (10), and β-allyl α-keto esters (11), formed as single diastereomers from sugar derivatives (7a) or (7b). Although esters (11) could be derived by C-allylation of magnesium enolates (8), these have previously been shown to undergo exclusively O-allylation.…”

Microwave-Assisted Claisen and Aza-Claisen Rearrangements

“…Craig et al demonstrated the utility of the method in the synthesis of homoallylic sulfones 10a through a decarboxylative CR reaction (Scheme(3))[53][54]. The transformations could be carried out in the presence of N,Obis(trimethylsilyl)acetamide (BSA) (1.0 equiv) and potassium acetate (0.1 equiv) by 15 h reflux in toluene, while microwave irradiation requires only 3 min exposure in the presence or absence of solvent.…”