Claisen-Johnson-Ireland

Claisen, Carrol rearrangement, Eschenmoser-Claisen, Johnson-Claisen and Ireland-Claisen rearrangements/Mislow-Evans rearrangement... 

Equilibrating mixtures of allylic azide-containing allylic alcohols or allylic 2-tolylsulfonylacetic esters undergo Johnson-Claisen or Ireland-Claisen rearrangement to give unsaturated y-azido esters and acids, respectively (Scheme 8). ... 

Claisen Rearrangement Eschenmoser-Claisen Rearrangement Johnson-Claisen Rearrangement Ireland-Claisen Rearrangement... 

In a recent synthesis of the aspidosperma alkaloid aspidophytine 396, Fukuyama used a Claisen-Johnson rearrangement to introduce stereoselectively the quaternary center at C-20 (Scheme 6.65) [94]. In a previous synthesis of this alkaloid by Corey, the configuration of same stereogenic center was controlled via a Claisen-Ireland rearrangement [95]. 

In a recent study [105], the same group applied the Claisen-Johnson rearrangement to D-glucose derived spirocyclic substrate 437. This reaction afforded a mixture of stereoisomers. It is worthy of note that the selectivity of the rearrangement is highly dependant upon the substitution of the orthoester (Scheme 6.72). The Claisen-Ireland rearrangement was inoperative with these glucose derivatives. 

Scheme 6.76). Heathcock developed a synthetic strategy wherein the 1,2-stereoselection obtainable from aldol reaction is parlayed by a subsequent Claisen rearrangement into 1,4 and 1,5-stereoselection [118]. Claisen-Johnson, Claisen-Eschenmoser and Claisen-Ireland rearrangements were examined in this study. However the orthoester Claisen-Johnson rearrangement was not the most convenient in this case. The rather harsh reaction conditions often led to dehydration and other byproducts. An example of this rearrangement is given in Scheme 6.76. 

In the development of a new strategy using Claisen-Ireland ring contraction of large ring lactone followed by transannular Diels-Alder cycloaddition, Roush [119] prepared the tetraene diester 490 through a Claisen-Johnson rearrangement (Scheme 6.76). 

The Claisen rearrangement, discovered in 1912, has proven to be a powerful tool for the stereoselective generation of C—C bonds69. It is widely employed in complex multistep syntheses (see, for example, References 86-89) and has inspired many variations, including the Carroll (1940), Eschenmoser (1964), Johnson (1970), Ireland (1972) and Reformatsky-Claisen (1973) reactions69. 

In this section, the aliphatic Cope and Claisen rearrangements, as depicted in the transformation of I to 2 in Scheme 2, are discussed, as well as variations of the latter (i.e.. Johnson-Claisen, Ireland-Claisen, Reformatsky Claisen, F.schenmoser-Claisen. Ficini Claisen, and hetero-Claisen rearrangements). When X is oxygen, replacement of Cl and C2 with an aromatic ring... 

The Johnson Ortho Ester Rearrangement 7.22.8 The Ireland Silyl Ester Enolate Rearrangement 722.9 Charge-accelerated Claisen Rearrangements 7.22.10 Cat ysis of Claisen Rearrangements 722.11 Competitive Rearrangements... 

Most [3,3]-sigmatropic rearrangements take place thermally, and the Cope, oxy-Cope and Claisen rearrangements are among the most important rearrangements in this class. Important variants of the Claisen rearrangement include the Johnson modification via orthoesters, the Eschenmoser modification via ketene N,O-acetals, the Ireland modification via ketene silylacetals and the Corey modification via boron ester enolates [696], The aza-Claisen rearrangement has also seen... 

Other variants of Claisen rearrangement [31] (Kazmaier [32], Ireland [33], and Johnson [34]) gave no rearranged product. 

Scheme 13.30 Sequential Johnson-Claisen and Eschenmoser-Claisen rearrangements. Scheme 13.31 Double Ireland-Claisen rearrangement reactions.

The Eschenmoser or Ireland variations of the Claisen rearrangement used by Corey and co-workers gave very good yields of the substituted hex-2-enopyranoside (73). On the other hand, Hernandez used the Johnson variation of the Claisen and obtained lower yields. This is not surprising in view of the pronounced sensitivity of hex-2-enopyranosides (e. g. 73) to acid conditions such as those required in this variation. 

In 1988 Heathcock reported the Johnson, Eschenmoser and Ireland-Claisen rearrangements of ketene acetals derived from chiral non-racemic allyUc alcohols (Scheme 4.23) [25]. The alcohols were themselves derived from Evans aldol additions. While the Johnson and Eschenmoser rearrangements were used to iUus-... 

The Claisen rearrangement of bis-allyl vinyl ethers and related systems has been studied by several groups [98]. Modest to high levels of regioselectivity were obtained in the parent Claisen as well as Johnson, Eschenmoser and Ireland variants of the reaction. Parker and Farmar applied the ester enolate variant of the Ireland-Claisen rearrangement of a bis-aUylic ester to the synthesis of biflora-4,10(19),15-triene, using the rearrangement to install the 1,3-diene component for a subsequent intramolecular Diels-Alder reaction [99]. 

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