Bandil (Hive Bee)
05-14-03 06:42
No 433139
      Reduction of carboxylic acids & esters to alkane  Bookmark   

Hi!

Just found an interesting article i would like to read:

From advance organic chemistry by Jerry March, 4. ed. pp.1214:

9-43:

         (C5H5)TiCl2
RCOOR'----------->RCH3 + R'OH

"The reagent titanocene dichloride reduces carboxylic esters and acid in a different manner from that of 0-81, 9-40, or 9-42. The product are the alkane RCH3 and the alcohol R'OH. The mechanism probably involves an alkene intermediate

The reference to this is: van Tamelen; Gladys J. Am. Chem. Soc. 1974, 96, 5290.

Does anyone have access to this article? It would be really nice to read it, as titandodecene is not super expensive(if the yeilds are half descent that is).

Regards
Bandil

Cops are not there to help you, they're there to bust you.
 
 
 
 
    ChemisTris
(Hive Bee)
05-14-03 12:36
No 433162
      here is the pdf & article
(Rated as: excellent)
 Bookmark   

http://mishmashblue.tripod.com/ja00823a065.pdf
smile

Direct Conversion of Aldehydes, Esters, and 1,2-Oxides to Alkanes with Carbon Skeleton Preservation J. Am. Chem. Soc. 96, 5290 (1974)


Sir:
Remarkable for its facile, reversible binding of molecular nitrogen as a reducible ligand, the titanocene system [(C5H5)2Ti]1-21, 2 also effects the catalytic hydrogenation of olefins2 and the reductive decyanation of alkyl nitriles.3 We now report the titanium-based, direct conversion of aldehydes, esters, and 1,2-oxides to

RCHO ---> RCH3


RCOOR' ---> RCH3(+R'OH)


R R" R      R"
 \     /         \    /
  C - C   --->    CH-CH
 / \ / \         /    \
R'  0   H R'     H



saturated hydrocarbons with preservation of the carbon skeleton,4 reductions occurring in good yield at room temperature.
Although this type change can be realized through the Wolff-Kishner (basic) or Clemmensen (acidic) reaction on aldehydes, the corresponding transformations with esters and l,2-oxides 5 are, as far as we know, not precedented.

The procedure is illustrated with dodecanal, the carbonyl compound selected for various studies on the aldehyde reaction. In a glove box or Schlenk apparatus rigorously free of oxygen,6 2.5 g (10 mmol) of recrystallized (CHCl3) titanocene dichloride, 0.5 g (22 mmol) of fine sodium sand, 12 ml of dry, deoxygenated benzene (purified by distillation from sodium benzophenone ketyl), and a 1-in. Teflon stirring bar were added to a 50-m1 round-bottomed flask. The mixture was stirred at the highest possible speed until the supernate turned a dark green (10-48 hr) and then was immediately filtered with benzene washing through a glass frit, thereby being freed from NaCl, unreacted sodium, and insoluble polymeric titanium species (CAUTION: the gray-black residue warms up and can ignite upon exposure to air). To the dark greenish filtrate7 was added 36.8 mg (0.2 mmol) of dodecanal. After being stirred 72 hr, 5 ml of degassed water was added to the mixture while maintaining inert atmosphere conditions; over the course of 4-8 hr, the reaction mixture turned a dark purple. The benzene was removed under reduced pressure, and the product was extracted with petroleum ether. Drying, concentration, and silica gel chromatography yielded 24.1 mg of pure dodecane (71 %), characterized by gas chromatography (gc) and mass spectrometry. About 15-20% dodecanol was formed concurrently.

In experiments with molar ratios of starting titanocene dichloride-dodecanal less than 10:1, much less total product is recoverable. At temperatures either lower or higher than ambient, considerably more alcohol and much less alkane are generated.
By means of the outlined procedure, decanal and 2-methylundecanal were converted in similar yield to decane and 2-methylundecane, respectively. Ketones afforded much less hydrocarbon (7-25 %) and correspondingly larger amounts of alcohol (up to 74 %) and starting materials (Table I).

When subjected to the above conditions, many esters are reduced to hydrocarbons in acceptable yields (see Table I). Although in poorer yields, dodecanoyl chloride (18-45%), dodecanoic acid (2 %), and lithium dodecanoate (25 %) were transformed to dodecane.
1,2-Oxides are reduced to alkanes (Table I) under the same conditions used for aldehydes and esters. Also, as single case examples, nonane (27 %) and dodecane (98%) were formed respectively from nonyl isocyanide and dodecyl bromide. Dodecane is produced from both dodecyl mercaptan (20%) and didodecyl sulfide (11-13 %). Only starting material was recovered when reduction was attempted with alcohols, alkoxides, or acyclic ethers.
That the reagent employed in the described reactions

Table I. Reduction of Carbonyl Compounds and 1,2-Oxides:
         Starting material                     Product            % Yields
- Aldehydes & Ketones -    
     
Dodecanal Dodecane 71 b
  Dodecanol 15-20
     
Decanal Decane 61
  Decanol 11
     
2-Methylundecanal 2-Methylundecane 44
     
trans-2-Decanal Decane 0-22
  1-Decene 0 (zero)
  Decanol 0-5
     
p-Methoxybenzaldehyde p-Cresol methyl ether 0 (zero)
     
2-Undecanone Undecane 3-20
  2-Undecanal 48-72
     
6-Dodecanone Dodecane 7-25
  6-Dodecanol 32-70
     
2-Adamantanone 2-Adamantanol 72-74
     
- Esters -    
Methyl dodecanoate Dodecane 66
  Dodecanol 9
     
Ethyl dodecanoate Dodecane 64-69
  trans-2-Dodecene 0-4
  Dodecanol 9-14
     
Decyl dodecanoate Dodecane 58
  trans-2-Dodecene 2
  Dodecanol 7
  Decanol 70
     
Methyl trans-2-decenoate Decane 3-35
  1-Decene 0 (zero)
  Decanol 0-2
     
gamma-Decalactone 4-Decanol 60
     
Methyl trans-myrtanoate trans-Pinane 17
  trans-Myrtanol 28
     
Methyl 1-adamantane-carboxylate 1-Methyladamantane 0 (zero)
  Adamantylcarbinol 35-64
     
Methyl 5 Beta-cholanate 5 Beta-Cholane 56 b
     
Methyl p-isopropylbenzoate p-Isopropyl benzyl alcohol 82
- Oxides -    
1-Decene oxide Decane 68-81
  1-Decanol 4-9
     
trans-2-Decene oxide Decane 58
     
2-Methyl-1-undecene oxide 2-Methylundecane 52
     
alpha-Pinene oxide cis-Pinane 10
     


a Product identity and yields were determined by gc and mass spectral methods.
b Yields also based on isolated product.

is extraordinary is revealed by reduction attempts with other transition metal species. No dodecane (or dodecene) was formed from dodecanal when the following systems were assayed: (C5H5)2MoH2,
(C5H5)2MoH2-isoprene,8 TiH2, VH, Na, VCl2_3-Na,
MoCl3-4,-Na. A few per cent of alkane was detected after reaction with (C5H5)2MoH2 with a catalytic amount of HCl, (C5H5)2TaH3 (80),9 or Fe(acac)3Na.
Various observations signify that the reduction of aldehydes and esters to alkanes involves olefin intermediates. Interruption of a dodecanal reaction after 3 hr revealed 10-15% 1- and 2-dodecene with 37-44% dodecane. As reaction time increased, the yield of dodecane became optimal while the amount of olefin approached zero. Olefin reduction during the overall reaction is consistent with the separate conversion of ldecene by the usual titanocene preparation to decane in 76-89% yield. When a dodecanal reduction was carried out starting with (C5H5)(C5D5)TiCl2, highly deuterated decane (d1-d16) was formed (as evidenced by gc and mass spectral data), thereby revealing extensive exchange of titanocene deuterium, presumably with hydrogen of intermediate olefin. Further, when an aliquot removed after 3 hr from a dodecanal reaction was quenched with D2O, ca. 50% of the dodecane contained two deuteriums (mass spectral), while remaining alkane and 1-dodecene possessed deuterium at ca. natural abundance levels. However, reactions quenched with D20 after 72 hr featured substantially less deuterium incorporation. No deuterium was transferred to hydrocarbon product from benzene-d6 solvent. The foregoing results indicate the formation of intermediate titanium-bound olefin, which can be converted to alkane by D20-H20 or by hydride from cyclopentadienide ligands. Similar deuterium labeling results were secured with ethyl dodecanoate, thus sug-


RR'CHCOOR" ---> RR'CHCHO -->
RR'C=CH2 + [(C5H5)2Ti]n RR'C=CH2 [(C5H5)2Ti]n --> RR'CHCH3,


gesting that with esters initial reduction to the aldehyde level is followed by steps identical with those involved in reductions starting with aldehydes. In keeping with the suggested scheme, no hydrocarbon was formed from aldehydes and esters which would not be expected to form olefins, including aromatic aldehydes and ladamantane carboxylic acid methyl ester. Although the driving force for the conversion of aldehyde to olefin must be formation of the titanium-oxygen bond by a reactive titanocene species, the exact mechanism of deoxygenation has not been established. That epoxide deoxygenation conforms to the pattern is revealed through D20 quenching of the 1-decene oxide reaction after 3 hr, whereupon 1-decene, 2-decene, and decane emerged with deuterium levels at or slightly above natural abundance.

Acknowledgment.
Financial support was provided by NIH Grant GMl3797.

E. E. van Tamelen,* J. A. Gladysz

Department of Chemistry, Stanford University

Stanford, California 94305

Received May 11, 1974



Refs:
(1) E. E. van Tamelen, R. B. Fechter, S. W. Schneller, G. Boche, R. H. Greeley, and B. Akermark, J. Amer. Chem. Soc., 91, 1551 (1969); (b) E. E. van Tamelen, D. Seeley, S. Schneller, H. Rudler, and W. Cretney, ibid., 92, 5151 (1970); (c) J. E. Bercaw, R. H. Narvich, L. G. Bell, and H. H. Brintinger, ibid., 94, 1219 (1972).
(2) E. E. van Tamelen, W. Cretney, N. Klaentschi, and J. S. Miller, J. Chem. Soc., Chem. Commun., 481 (1972).
(3) E. E. van Tamelen, H. Rudler, and C. Bjorklund, J. Amer. Chem. Soc., 93, 7113 (1971).
(4) For the preparation of alkanes through aldehyde or acyl chloride decarbonylation, see J. Tsuji and K. Ihno, Synthesis, 1, 157 (1969).
(5) For two-electron reductions of epoxides to alkenes, see K. B. Sharpless, M. A. Umbreit, M. T. Nieh, and T. C, Flood, J. Amer. Chem. Soc., 94, 6538 (1972), and references cited therein.
(6) Catalytic amounts of oxygen inhibit this reaction and for obvious reasons, nitrogen must also be excluded.
(7) A brown color indicates incomplete reduction and a yellow color reflects oxygen contamination of the reaction mixture, which then should not be used.
(8) These conditions are believed to produce a molybdenocene intermediate: B. R, Francis, M. L. H. Green, and G. G. Roberts, Chem. Commun., 1290 (1971); M. L. H. Green and P. J. Knowles, J. Chem. Soc. A, 1508 (1971).
(9) In refluxing benzene, (C6H5)2TaH3, evolves H2 to give an intermediate isoelectronic with titanocene: E, K. Barefield, G. W. Parshall, and F. N. Tebbe, J. Amer. Chem. Soc., 92, 5235 (1970).


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    Aurelius
(Hive Addict)
05-14-03 14:25
No 433192
      Oxygen (Air)  Bookmark   

Yes, but it appears to react with air.  "rigorously" excluding oxygen?  not exactly kitchen chem, but interesting none-the-less.
 
 
 
 
    Bandil
(Hive Bee)
05-15-03 04:51
No 433314
      It doesn't seem like a totally evil chemical...  Bookmark   

It doesn't seem like a totally evil chemical like LAH, bromine or DMS according to chemfinder. LAH is also quite sensitive to moisture etc, but that is still used on the kitchentable by many folks... Maybe it's just the authors being overly carefull :)

I think this compound deserves it's go at some tryptophan. Always hated the oxygens on that compound and think they deserve to be removed ASAP!!!

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    Prometheuz
(Newbee)
05-15-03 06:03
No 433325
      Relatively harmless  Bookmark   

It actually seems to be a relatively benign chemical, at least compared to LAH and Br2. Interesting. But I could imagine that stuff would be rather expensive.
Datasheet (http://ntp-server.niehs.nih.gov/htdocs/CHEM_H&S/NTP_Chem1/Radian1271-19-8.html)

To fathom Hell or soar angelic
Just take a pinch of psychedelic
 
 
 
 
    Bandil
(Hive Bee)
05-15-03 06:15
No 433328
      It says here: This chemical is sensitive to...  Bookmark   

It says here:

      This chemical is sensitive to exposure to moisture [058,062,269,275].
 It is stable in dry air Post 062 (not existing).  UV spectrophotometric stability screening
 indicates that solutions of this chemical in 95% ethanol are stable for less
 than two hours (RAD).  Fresh solutions should be prepared before each use.


So, as prometheus says, it looks like playdough compared to other chemicals.

It's quite soluble in DMSO(100 mL/mL). Could it be preferable to do the reductions in DMSO over benzene?

Does anyone have an compentent estimate of the yeilds if some rouge bandit where to use it on tryptophan or 5-HTP?

Regards
Bandil

Cops are not there to help you, they're there to bust you.