Cyclobutanones for the stereoselective synthesis of bifunctional macrolide intermediates

Fráter, Georg; Müller, Urs; Günther, Wulf

doi:10.1016/s0040-4039(01)91542-4

Cited by 12 publications

(1 citation statement)

References 9 publications

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“…Later, we turned our attention to the more classical way of stereochemical control, that is to the stereoselective synthesis of small-ring compounds, which can be cleaved to the desired open-chain compound. Thus, bifunctional C, units of (R*,R*)and (R*,S* )-configuration were synthesised [2] starting with a [2 + 21-ketene cycloaddition.…”

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[2 + 2] cycloaddition of optically active ketenes. Synthesis of (−)‐blastmycinone. Preliminary Communication

Fráter

Müller

Günther

1986

Helvetica Chimica Acta

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2 + 21 Cycloaddition of (menthy1oxy)methylketene (2) to cis-ethyl propenyl ether showed a ca. 3:l diastereoselectivity. A two-step transformation of the thermodynamically more stable adduct 4 furnished the (2R*,3R*)compound 5 with ca. 50% e.e. (Scheme I). The analogous reaction sequence with cis-benzyl 1-hexenyl ether (9) and 2 showed a ca. 5.1 diastereoselectivity in 10 and 11 (Scheme 2). Absolute configuration of C(3) and C(4) in 11 has been proved by converting it to (-)-hlastmycinone. Accordingly, the preferred transition state has been deduced as 15.

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confidence: 99%

[2 + 2] cycloaddition of optically active ketenes. Synthesis of (−)‐blastmycinone. Preliminary Communication

Fráter

Müller

Günther

1986

Helvetica Chimica Acta

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TheBeckmann Reactions: Rearrangements, Elimination–Additions, Fragmentations, and Rearrangement–Cyclizations

Gawley

1988

Organic Reactions

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The Beckmann rearrangement, the acid‐mediated isomerization of oximes to amides, was discovered by Beckmann in 1886. As one of the oldest and most familiar transformations in organic chemistry, it has been reviewed several times. What has become known as the Beckmann fragmentation was in fact first observed by Wallach in 1889 but was not developed extensively until the 1960s. It has been referred to by several names over the years and has also been reviewed. The rearrangement cyclization is the intramolecular cyclization of a nitrilium ion generated by Beckmann rearrangement from an oxime. Within the context of an aromatic terminator, the process was first reported by Goldschmidt in 1895. Wallach reported the first case of an aliphatic terminator in 1901, although the reported structure was incorrect, and Perkin was apparently the first to observe a heteroatom terminator, but he also reported an incorrect structure. The process has been exploited only quite recently. This chapter is an update of these reactions, last reviewed in this series in 1960. Not covered are transformations that have been labeled Beckmann‐type reactions but are mechanistically unrelated. The most prominent of these is the so‐called photochemical Beckmann rearrangement, first observed by De Mayo in 1963 and discussed in a review several years ago. Worthy of mention, however, is the fact that many oximes that suffer fragmentation under acidic conditions undergo rearrangement when photolyzed. Throughout this chapter, the ( E ) and ( Z ) nomenclature is used to describe oxime geometry.

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Beckmann Rearrangement and Beckmann Fragmentation

2010

Comprehensive Organic Name Reactions and Reagents

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The rearrangement of an oxime to its corresponding amide in the presence of an acid and is generally known as the Beckmann rearrangement. The oxime is also formed by the reaction of a ketone with hydroxylamine. The conversion of cyclohexanone oxime into e‐caprolactam is known to be an important component for the fabrication of nylon 6. The Beckmann rearrangement of oxime derivatives proceeds stereospecifically, and the stereo‐configuration of the migrating group is retained. This rearrangement has been applied to the construction of a variety of nitrogen‐containing compounds. Certain oximes, those having a quarternary carbon anti to the hydroxyl, have been reported to undergo the rearrangement to form nitriles instead of amides. This type of transformation is called the Beckmann fragmentation, which has been used in modification of steroids. Other oximes, such as the bridged bicyclic ketoximes and oximes with an electron‐donating substituent at the α‐carbon, also undergo fragmentation.

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Cyclobutanones for the stereoselective synthesis of bifunctional macrolide intermediates

Cited by 12 publications

References 9 publications

[2 + 2] cycloaddition of optically active ketenes. Synthesis of (−)‐blastmycinone. Preliminary Communication

[2 + 2] cycloaddition of optically active ketenes. Synthesis of (−)‐blastmycinone. Preliminary Communication

TheBeckmann Reactions: Rearrangements, Elimination–Additions, Fragmentations, and Rearrangement–Cyclizations

Beckmann Rearrangement and Beckmann Fragmentation

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