An Oxidative [2,3]-Sigmatropic Rearrangement of Allylic Hydrazides

Synthetic routes to α,α‐disubstituted allylamines have been examined. Racemic compounds were conveniently prepared by thermal Overman rearrangements of primary allylic alcohols with trisubstituted double bonds, but rearrangement of these substrates using the only commercially available compound known to catalyze enantioselective Overman rearrangements, the cobalt oxazoline palladacycle (R)‐COP‐Cl, failed. Instead, optically active secondary allylic alcohols with trisubstituted double bonds, obtained by Corey–Bakshi–Shibata reduction of the corresponding methyl ketones, were synthesized and converted into α,α‐disubstituted allylamines through a thermal Overman rearrangement or an allylic‐cyanate‐to‐isocyanate rearrangement. High chirality transfer (90–99 %) was obtained for both reaction sequences, but the yields were greatly improved when the allylic‐cyanate‐to‐isocyanate rearrangement was used.

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“…for C 12 H 16 LiO [M + Li] + 183.1361; found 183.1370. The NMR spectroscopic data are in good agreement with those reported before …”

Section: Methodssupporting

confidence: 91%

Rearrangement Reactions Leading to Optically Active α,α‐Disubstituted Primary Allylamines

2017

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“…One possible alternative is the pathway involving nitrene intermediates 8 (Scheme ). However, this is not true because the separately‐formed nitrene 8 a generated by treating 3 a with iodosylbenzene19 gave the [2,3]‐rearrangement product 9 a along with only a trace amount of 7 a [Eq. (2)].…”

Section: Methodsmentioning

confidence: 99%

Substitution of Two Fluorine Atoms in a Trifluoromethyl Group: Regioselective Synthesis of 3‐Fluoropyrazoles

2012

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Replacing the fluorine: 3‐Fluorinated pyrazoles were regioselectively synthesized by sequential substitution reactions of 2‐trifluoromethyl‐1‐alkenes (see scheme). SN2′‐type reactions of 2‐trifluoromethyl‐1‐alkenes with deprotonated tert‐butoxylcarbonyl‐ or arylhydrazines afforded 1,1‐difluoro‐1‐alkenes, which were tosylated and then treated with NaH to give the desired 3‐fluoropyrazoles.

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“…The absolute configuration of the product was assigned by X-ray crystallography (see section 8). The (2S,3R) enantiomer was prepared according to the general procedure using (S,R)-13 (10 mol %) from (E)-3methyl-5-phenylpent-2-en-1-ol (4). From a 1.0 mmol (176 mg) scale bromochlorination employing (S,R)-13 (43 mg, 0.1 mmol) was isolated product (−)-S4 in 94% yield (272 mg) of 89% ee as an 8:1 mixture of constitutional isomers after purification by flash column chromatography (25 g silica gel, 5 to 20% ethyl acetate/hexanes gradient) along with 18 mg (5% yield) of the corresponding dibromide.…”

Section: Synthesis and Characterization Of Dihalide Products (R)-(−)-mentioning

confidence: 99%

Catalytic Chemo-, Regio-, and Enantioselective Bromochlorination of Allylic Alcohols

et al. 2015

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Herein we describe a highly chemo-, regio-, and enantioselective bromochlorination reaction of allylic alcohols, employing readily available halogen sources and a simple Schiff base as the chiral catalyst. The application of this interhalogenation reaction to a variety of substrates, the rapid enantioselective synthesis of a bromochlorinated natural product, and preliminary extension of this chemistry to dibromination and dichlorination are reported.

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An Oxidative [2,3]-Sigmatropic Rearrangement of Allylic Hydrazides

Cited by 30 publications

References 44 publications

Rearrangement Reactions Leading to Optically Active α,α‐Disubstituted Primary Allylamines

Rearrangement Reactions Leading to Optically Active α,α‐Disubstituted Primary Allylamines

Substitution of Two Fluorine Atoms in a Trifluoromethyl Group: Regioselective Synthesis of 3‐Fluoropyrazoles

Catalytic Chemo-, Regio-, and Enantioselective Bromochlorination of Allylic Alcohols

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