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All 7 posts   Subject: hydrazone from a,b conj aldehyde ?   Please login to post   Down

 
    stratosphere
(Newbee)
10-17-03 19:41
No 465246
       hydrazone from a,b conj aldehyde ?     

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? 		 
 
 
 
    Aurelius
(Active Asperger Archivist)
10-17-03 22:14
No 465285
       Hydrazones of Cinnamaldehyde     

No.

https://www.rhodium.ws/chemistry/cinnamaldehyde.html
Act quickly or not at all. 		 
 
 
 
    Rhodium
(Chief Bee)
10-17-03 23:01
No 465290
User Picture  		      Ketone deoxygenation TsNHNH2/BzOH/BH3.THF
(Rated as: excellent) 		    

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.rhodium.ws/pdf/carbonyl.deoxygenation.tsnhnh2-bh3-phcooh.pdf) 		 
 
 
 
    GC_MS
(Hive Addict)
10-18-03 09:49
No 465379
User Picture  		      And don't forget     

You seem to forget about ChemisTris' γ-asarone synthesis using 2,4,5-trimethoxycinnamaldehyde (which in turn has been prepared from β-asarone) and TsNHNH2: Post 445839 (ChemisTris: "Conversion of B-asarone into [gamma] asarone", Chemistry Discourse) wink
Advanced clitoris massage specialist. 32 years of experience. PM me for a "sample". 		 
 
 
 
    stratosphere
(Newbee)
10-18-03 22:24
No 465484
       a perhaps naive question: would the absesnce...     

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
(Chief Bee)
10-19-03 01:32
No 465521
User Picture  		      NaBH3CN Ketone/Aldehyde Deoxygenation
(Rated as: excellent) 		    

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 ,-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.rhodium.ws/pdf/cinnamaldehyde2propenylbenzene.pdf)
DOI:10.1016/0040-4039(95)00252-8

Abstract
A simple and convenient procedure for a highly chemoselective reductive deoxygenation of ,-unsaturated ketones and allyl alcohols to olefins by sodium cyanoborohydride and boron trifluoride etherate in dry THF is described.



Reductive, selective deoxygenation of acylbenzo[b]furans, aromatic aldehydes and ketones with NaBH3CN-TMSCl
Vernon G. S. Box and Panayiotis C. Meleties
Tetrahedron Letters 39(39), 7059-7062 (1998) (https://www.rhodium.ws/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.



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.rhodium.ws/pdf/deoxygenation.nabh3cn-bf3-et2o.pdf) 		 
 
 
 
    moo
(Hive Addict)
07-29-04 20:56
No 522534
       Propenylbenzene from cinnamaldehyde
(Rated as: excellent) 		    

There are two references discussing the Wolff-Kishner reduction of cinnamaldehyde to propenylbenzene.



Reduction of Steroid Ketones and other Carbonyl Compounds by Modified Wolff--Kishner Method
Huang-Minlon
J. Am. Chem. Soc. 71, 3302 (1949)



General procedure

The reduction has been carried out by procedures similar to those described in previous papers1,2. Thus a mixture of the starting material, diethylene or triethylene glycol (Note 1), alkali hydroxide and 85% hydrazine hydrate (Notes 2 and 3) was refluxed for about half an hour and the condenser was then removed to allow the aqueous liquor to evaporate and the temperature of the reaction mixture to rise to about 200°. In cases where either the starting material or the reduced product is volatile a takeoff adapter was used instead of removing the condenser to evaporate aqueous liquor. After refluxing at this temperature for about two hours the reaction mixture was cooled, diluted with water (Note 4) and the separated reaction product was filtered or extracted with ether (Note 5).
 
NOTE 1. The amount of diethylene glycol or triethylene glycol used can be varied according to the solubility of the carbonyl compound or its hydrazone formed during the reaction so that a clear or nearly clear reaction mixture is obtained during the heating period. Sometimes it is advisable to dissolve the carbonyl compound in alcohol before addition of glycol and other reagents, e.g., in the case of cholestanone and cholestenone.
NOTE 2. The amount of alkali hydroxide used is about 10% to the volume of the glycol used and the amount of 85% hydrazine hydrate used is always in excess (3 moles or more).
NOTE 3. In reduction of alkali sensitive compounds such as aldehydes, α,β-unsaturated ketones and those carbonyl compounds in which the carbonyl group is adjacent to an asymmetric center it is advisable to reflux the glycol solution of starting material with hydrazine hydrate for about half an hour and then add a concentrated aqueous solution of alkali hydroxide slowly as described previously.
NOTE 4. If the reduced product is acidic, it is obtained by acidifying the cooled reaction mixture with dilute hydrochloric acid.
NOTE 5. In cases where the starting material contains methoxy group the crude reduced product was remethylated with dimethyl sulfate.
NOTE 6. Most of the technical steroid ketones were recrystallized before reduction, since otherwise the yield is sometimes unsatisfactory. The yields of reduced products given in Table I are on the basis of pure products for which the melting points are given.
NOTE 7. In cases where the carbonyl compound is unstable and difficult to purify such as a-naphthaldehyde the hydrazone or semicarbazone can be taken as starting material for reduction.
                                                                                                       
(I took the liberty to omit all the steroid ketones from the table and leave the ones bees might be more interested in)

Table 1.
Compound Product B. p. °C. Yield,
%		 n25D
Vanillin 3,4-Dimethoxy-1-methylbenzenea 133-135 (50 mm.) 77.3 1.5257
Veratraldehyde 3,4-Dimethoxy-1-methylbenzene 122-124 (27 mm.) 81 1.5259
Cinnamic aldehyde Propenylbenzene 176-178 (755 mm.) 70 1.5464
aOn methylation of the crude reduced product with dimethyl sulfate.

1 Huang-Minlon, J. Am. Chem. Soc. 68, 2487 (1946)
2 Huang-Minlon, J. Am. Chem. Soc. 70, 2802 (1948)



The other ref is Helv. Chim. Acta 35, 780 (1949) where the hydrazone of cinnamaldehyde is first formed separately and then decomposed with alcoholic alkali by heating in a pressure tube.
fear fear hate hate 		 
 

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