Synthetic applications of metal halides. Conversion of cyclopropylmethanols into homoallylic halides

McCormick, John; Barton, Donald

doi:10.1021/jo01301a003

Cited by 55 publications

(25 citation statements)

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“…Engl. 31 (1992) To prepare a suitable substrate for the proposed Reformatsky double annulation process, we started with enol ether 58, which was conveniently prepared from the corresponding p-keto ester. Alkylation of the lithium enolate of 58 with homogeranyl iodide (36) provided 59, which was reduced with lithium aluminum hydride to alcohol 60 (Scheme 19).…”

Section: Stealing Another Page From Mother Nature: Conversion Of the mentioning

confidence: 99%

The Enchanting Alkaloids of Yuzuriha

Heathcock

1992

Angew. Chem. Int. Ed. Engl.

149

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The oriental plant Yuzuriha (Daphniphyllurn macropodurn) elaborates a fascinating family of polycyclic, squalene-derived alkaloids that provide a test for state-of-the-art methods of organic synthesis. The intriguing structures of these natural products have inspired us to design and explore two rather different approaches for their laboratory synthesis. This article recounts and contrasts these two different syntheses. The first approach was based on a method of synthetic design that emphasizes efficient construction of the polycyclic skeleton of the molecule (Corey's "network analysis"). A strategic bond was identified and the synthesis planned around the late formation of this bond. The synthesis that was designed by this approach proceeded smoothly until the point where it was necessary to remove functional groups that had been incorporated solely for the purpose of forming the strategic bond. Although the problems were eventually overcome, the resulting synthesis was too long and did not control the configuration of one of the stereocenters. The second approach was based on a possible biosynthesis of one of the alkaloids and provided surprisingly easy access to the simpler members of the family. The success of this synthesis led to a concrete proposal about the biosynthesis of the alkaloids and to the discovery of the astonishing transformation depicted in Scheme 27. In this marvelous reaction, an acyclic squalene derivative is converted by successive treatment with ordinary commodity chemicals into a pentacyclic alkaloid. The transformation involves the formation of four carbon-wbon bonds, two carbon-nitrogen bonds, and one carbon-hydrogen bond!

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Section: Stealing Another Page From Mother Nature: Conversion Of the mentioning

confidence: 99%

The Enchanting Alkaloids of Yuzuriha

Heathcock

1992

Angew. Chem. Int. Ed. Engl.

149

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“…Unfortunately, in practice neither of these objectives was experimentally feasible and treatment of the alcohol 1 or its tosylate (both epimers separately) under a variety of acidic and solvolytic conditions failed to provide ring-opened products in spite of related literature precedent (5). Similarly, reaction of the bromide with magnesium, lithium, and zinc salts did not afford the desired ring-opened olefins although these reactions proceed readily with less complex systems (6). Likewise, the phosphonate prepared from 1 underwent reduction with lithium napthalide but carbon-carbon bond cleavage did not result.…”

Section: Introductionmentioning

confidence: 99%

A general synthesis of the tricyclo[4.4.0^1,6.0^5,9]decane (sinularene) and tricyclo[5.4.0^1,7.0^6,10]undecane (longifolene) ring systems by selective cleavage of bridged-ring cyclopropyl ketones

Attah-Poku¹,

Antczak²,

Alward³

et al. 1984

Can. J. Chem.

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Can. J. Chem. 62,1717(1984. The reactivity of the tetracyclic cyclopropyl compounds 1, 8, 9. 10. and 15 has been investigated and general routes to the "sinularene" and "longifolene" skeletons developed. Hydrogenolysis cleaves the least substituted cyclopropane bond ("a") to give the tricycl0[4.4.0'.~.0~~~]decane (sinularene) ring systems 5 and 6. Lithium-ammonia and zinc -zinc chloride reduction affords both tricyclic ketones 11 and 13 and 12 and 14 while chromium sulphate in I : I dimethyl formamide/water gives the tricycl0[5.4.0'~~.0~.'~']undecene (longifolene) skeleton 14 exclusively (cleavage of bond "b") from ketone 9.

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“…13 This material is readily available via cycloaddition of the acetylene 6 and the azide 7 , with the azide prepared from the alcohol 8 which in turn is readily available through a ring opening rearrangement of the cyclopropyl carbinol 9 . 14 Unfortunately, this rearrangement is known to give a mixture of olefin isomers in a ratio of ~3:1 ( E to Z ). 14 Variations in the reaction conditions did improve the ratio somewhat in favor of the E -isomer, 15 but the homonerol isomer was of special interest because the neryl analogue already was known to be more active than the corresponding geranyl isomer.…”

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confidence: 99%

“…14 Unfortunately, this rearrangement is known to give a mixture of olefin isomers in a ratio of ~3:1 ( E to Z ). 14 Variations in the reaction conditions did improve the ratio somewhat in favor of the E -isomer, 15 but the homonerol isomer was of special interest because the neryl analogue already was known to be more active than the corresponding geranyl isomer. 7 As the homoallylic bromides, the olefin isomers were not readily separable and so the mixture was carried forward to provide material for initial bioassays.…”

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confidence: 99%