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hydrazone from a,b conj aldehyde ?

Started by stratosphere, October 17, 2003, 09:41:00 PM

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stratosphere

im curious if a,b conjugation of cinnamaldehyde would interfere with hydrazone formation, if one were to attempt a wolff-kishner reduction of that material?


Rhodium

I couldn't find any literature refs mentioning cinnamaldehyde hydrazone (the "hydrazine imine" of cinnamaldehyde) being converted to either propenylbenzene or allylbenzene.

Nevertheless, I found one where cinnamaldehyde tosylhydrazone (from para-toluenesulfonylhydrazine) is reduced to allylbenzene in 85% yield (bis(benzoyloxy)borane, NaOAc*3H2O, CHCl3, 1h, 0°C).

The reagent bis(benzoyloxy)borane is nothing to be afraid of, as it is easily made in situ from benzoic acid and BH3.THF, the latter which in turn can be prepared by mixing equinormal amounts of NaBH4 and H2SO4 in THF.



A mild and convenient conversion of ketones to the corresponding methylene derivatives via reduction of tosylhydrazones by bis(benzoyloxy)borane
George W. Kabalka, S. Timothy Summers

J. Org. Chem. 46, 1217-1218 (1981)

(https://www.thevespiary.org/rhodium/Rhodium/pdf/carbonyl.deoxygenation.tsnhnh2-bh3-phcooh.pdf)

GC_MS

You seem to forget about ChemisTris' ?-asarone synthesis using 2,4,5-trimethoxycinnamaldehyde (which in turn has been prepared from ?-asarone) and TsNHNH2:

Post 445839

(ChemisTris: "Conversion of B-asarone into [gamma] asarone", Chemistry Discourse)
 ;)


stratosphere

a perhaps naive question:
would the absesnce of literature references then indicate that wolff-kishner style reduction would not work in this case?

The reagent bis(benzoyloxy)borane is nothing to be afraid of

what about formation of the tosyl hydrazone?

i wonder about the aldehyde->dithioacetal followed by H2/Ni reduction route?

Rhodium

would the absesnce of literature references then indicate that wolff-kishner style reduction would not work in this case?

Yes, unfortunately, that is most often the case, at least when it comes to simple molecules like these.

I have however found some one-step deoxygenations of cinnamaldehyde to propenylbenzene/allylbenzene using cyanoborohydride with a lewis acid additive, which also seems to deoxygenate benzaldehydes to methylbenzenes and aralkyl ketones to hydrocarbons in high yield:


Chemoselective reductive deoxygenation of https://www.thevespiary.org/rhodium/Rhodium/hive/hiveboard/picproxie_docs/000465246-file_lwwo.gif" title="View this image">,https://www.thevespiary.org/rhodium/Rhodium/hive/hiveboard/picproxie_docs/000465246-file_feqa.gif" title="View this image">-unsaturated ketones and allyl alcohols
A. Srikrishna, R. Viswajanani, J. A. Sattigeri and C. V. Yelamaggad

Tetrahedron Letters 36(13), 2347-2350 (1995)

(https://www.thevespiary.org/rhodium/Rhodium/pdf/cinnamaldehyde2propenylbenzene.pdf)
DOI:

10.1016/0040-4039(95)00252-8



Abstract
A simple and convenient procedure for a highly chemoselective reductive deoxygenation of https://www.thevespiary.org/rhodium/Rhodium/hive/hiveboard/picproxie_docs/000465246-file_lwwo.gif" title="View this image">,https://www.thevespiary.org/rhodium/Rhodium/hive/hiveboard/picproxie_docs/000465246-file_feqa.gif" title="View this image">-unsaturated ketones and allyl alcohols to olefins by sodium cyanoborohydride and boron trifluoride etherate in dry THF is described.

https://www.thevespiary.org/rhodium/Rhodium/hive/hiveboard/picproxie_docs/000465246-file_xnrs.gif" title="View this image">

Reductive, selective deoxygenation of acylbenzofurans, aromatic aldehydes and ketones with NaBH3CN-TMSCl
Vernon G. S. Box and Panayiotis C. Meleties

Tetrahedron Letters 39(39), 7059-7062 (1998)

(https://www.thevespiary.org/rhodium/Rhodium/pdf/deoxygenation.nabh3cn-tmscl.pdf)
DOI:

10.1016/S0040-4039(98)01519-6



Abstract
Aromatic aldehydes, ketones and acylbenzo[b]furans have been reductively deoxygenated with sodium cyanoborohydride and the mild electrophile chlorotrimethylsilane.

https://www.thevespiary.org/rhodium/Rhodium/hive/hiveboard/picproxie_docs/000465246-file_xnrs.gif" title="View this image">

A Simple and Convenient One Step Method for the Reductive Deoxygenation of Aryl Ketones to Hydrocarbons
Srikrishna, A.; Sattigeri, J. A.; Viswajanani, R.; Yelamaggad, C. V.

Synlett, (1) 93-94 (1995)

(https://www.thevespiary.org/rhodium/Rhodium/pdf/deoxygenation.nabh3cn-bf3-et2o.pdf)