No reaction was noted in the absence of triphenyl borate. The Ireland–Claisen rearrangement of silylketene acetals has proved to be a versatile route to derivatives of pent-4-en-1-oic acid. A modification of the Claisen rearrangement (of allyl vinyl ethers) in which allyl esters undergo a [3.3] sigmatropic rearrangement via their enolate anions or silyl enol ethers, resulting in γ,δ-unsaturated acids. The reaction proceeds through a boat TS to give the product 9.36. The Ireland–Claisen rearrangement has been used as a probe for the diastereoselectivity of nucleophilic attack on a double bond adjacent to a stereogenic center carrying a silyl group <2003OBC4005>. Rearrangement Temperature, Substituent Effects and Catalysis, Calculated vs. 1, 2 As depicted in Scheme 1, this method consists of two synthetic operations, namely O-silyl ketene acetal formation, followed by thermally induced [3,3]-sigmatropic rearrangement.Ireland demonstrated that Z-or E-selective O-silylation takes place on treatment of an … Encyclopedia of Physical Organic Chemistry. Marco-Contelles, in Comprehensive Organic Functional Group Transformations II, 2005. A competitive formation of the [1,3] transposition product was observed. This attractive strategy has also been proposed but using a radical-based Michael addition to a suitably functionalized allylic ester acrylate promoted by a combination of reagents such as manganese, lead dichloride, and trimethylsilyl chloride <1996JOC8728>. Number of times cited according to CrossRef: Acyclic 1,4-Stereocontrol via the Allylic Diazene Rearrangement: Development, Applications, and the Essential Role of Kinetic The Ireland–Claisen rearrangement is a type of Claisen rearrangement. The Journal of Organic Chemistry 1996, 61 (25) , 8728-8729. Palladium‐Catalyzed Allylic Alkylation of Doubly Deprotonated Carboxylic Acids, https://doi.org/10.1002/9783527610549.ch4. The intermediate aldehyde 13 can also serve as a precursor of 25(S)-dafachronic acid by use of the chain elongation-enantioselective hydrogenation process shown in Scheme2. Thus, allylic side-chains bearing remote vinylic electron-rich substituents rearranged preferentially (Scheme 92).218, When bis(allyl) 2-tosylmalonates were treated with the BSA/KOAc reagent combination under MWI, a double decarboxylative Claisen rearrangement sequence took place and provided substituted 1,6-heptadienes, which were subsequently transformed into polysubstituted pyridines (Scheme 93).219. A novel variant of the Ireland–Claisen rearrangement, in which an electron-withdrawing α-substituent is present at the ketene acetal skeleton, has been developed. The Ireland–Claisen rearrangement is a chemical reaction of an allylic ester with strong base to give an γ,δ-unsaturated carboxylic acid. Highly enantioselective Ireland-Claisen rearrangement of an achiral allyl ester can be effected via a chiral (cisoid) boron enolate as outlined in Scheme 42 (see also pages 110–111). Alkene Stereochemistry. The mechanism is therefore a concerted [3,3]-sigmatropic rearrangement which according to the Woodward–Hoffmann rules show … The silylketene acetals are then thermally rearranged ([3,3]-sigmatropic), via a chair-like transition state, to TMS esters, which on mild hydrolysis provide pent-4-en-1-oic acids (Equation (46)) <75TL3975, 76JA2868>. In two consecutive articles in the same journal issue, Piscopio <1998JOC3158> and Burke <1998JOC3160> reported enolate Claisen rearrangement and Ireland–Claisen rearrangement, respectively, on allyl-heteroatom-(C, O, S, N)-α-substituted acetates for the synthesis of intermediates that were transformed into carbocyles or heterocycles via ring-closing metathesis carbocyclization strategies. 9.40. The 1,6-conjugate addition of organocuprates to 2-propen-1-yl and 2-buten-1-yl 2-en-4-ynoates followed by in situ enolate capture with silyl electrophiles is followed by a quick [3,3]-sigmatropic rearrangement that yields 2-substituted methyl 3,4-dienoates <1997LA725> (Scheme 22). The Claisen rearrangement was first reported in 1912 and has become one of the most powerful methods for carbon–carbon bond formation in organic synthesis 1 as illustrated by the successful application of its numerous variants to natural product synthesis. Z. Gu, A. Zakarian, in Comprehensive Organic Synthesis II (Second Edition), 2014, Stoichiometric reagent control using chiral boron halides as depicted in Scheme 122 was developed for some of the early examples of enantioselective Ireland–Claisen rearrangement of achiral allylic ester. Stereoselective Synthesis of the CDE Ring System of Antitumor Saponin Scillascilloside E-1. Enantioselective Total Synthesis of .beta.-Elemene and Fuscol Based on Enantiocontrolled Ireland-Claisen Rearrangement. In a conformationally constrained system in which three or more atoms of allyl vinyl ether is part of a ring, the Claisen rearrangement proceeds preferably through a boat TS.47 To illustrate, let us consider the Johnson–Claisen rearrangement of a cyclic substrate 9.35 in which the three-atom allyl unit is part of the ring (Fig. The reaction proceeds through (E)-silyl ketene acetal which undergoes Claisen rearrangement via a boat TS to give, after desilylation, a diastereomeric acid. An Examination of the Scope and Stereochemistry of the Ireland–Claisen Rearrangement of Boron Ketene Acetals. The boron ketene acetal intermediates are formed through a soft enolization that obviates the use of strong bases and the intermediacy of alkali metal enolates. In Fig. Sequential 1,4-Addition and Ireland−Claisen Rearrangement Promoted by a Manganese−PbCl2−Me3SiCl System1. Similar results were achieved by brief exposure to MWI (Scheme 89).