Method for increasing the hydrogen:carbon ratio of an organic compound

A method for increasing the hydrogen:carbon ratio of an organic compound is disclosed. The organic compound can be one having any of the following functions: hydroxyl, carbonyl, epoxide, acetal, ketal, hemiacetal and hemiketal. The method involves introducing the organic compound and a silicon hydride into a liquid which is either chemically inert or acidic and introducing BF.sub.3 into the liquid to produce a reaction product having a higher hydrogen:carbon ratio than the starting organic compound. Examples of organic compound starting materials disclosed include undecanal, benzaldehyde, p-methylbenzaldehyde, p-chlorobenzaldehyde, p-methoxybenzaldehyde, p-cyanobenzaldehyde, p-nitrobenzaldehyde, 2-undecanone, cyclohexanone, 2-methylcyclohexanone, adamantanone, p-cyanoacetophenone, fluorenone, 1-naphthaldehyde, p-nitroacetophenone, fructose and cotton. The use, as the silicon hydride, of triethylsilane, (R)-(+)-1-naphthylphenylmethylsilane, dimethylethylsilane, phenylneopentylmethylsilane, and of tri-n-hexylsilane is disclosed, while methylene chloride is disclosed as the liquid in which the reaction is conducted.

BACKGROUND OF THE INVENTION 
The ability of organosilanes to transfer hydride selectively to a variety 
of carbocations is known, and has been utilized in the development of 
numerous synthetic techniques, e.g., the direct conversion of alcohols to 
hydrocarbons, which occurs when intermediate carbenium ions formed by 
reaction between alcohols and protic acids are captured by organosilanes. 
These known reactions are discussed in a paper* jointly authored by Merwyn 
G. Adlington, Michael Orfanopoulos and James L. Fry, and in the reference 
cited therein. The paper also describes briefly some of the experiments 
which constitute the genesis of the present invention. 
FNT * Tetrahedron Letters No. 34, pp. 2955-2958, 1976. 
BRIEF DESCRIPTION OF THE INVENTION 
Briefly stated, the present invention is based upon the discovery that the 
hydrogen to carbon ratio of certain organic compounds can be increased by 
a reaction involving a silicon hydride, a liquid which is either 
chemically inert or acidic and BF.sub.3. The organic compound, to be 
capable of undergoing such reaction, must have at least one hydroxyl, 
carbonyl, epoxide, acetal, ketal, hemiacetal or hemiketal function. When 
the hydrogen:carbon ratio is increased in accordance with the invention, 
the increase can be the consequence of the reduction of, for example, a 
carbonyl group to a CH.sub.2 group, or can be the consequence of the 
reduction of, for example, an aldehyde to the corresponding alcohol. The 
reaction appears to proceed stepwise, because whether a ketone, for 
example, is converted to an alcohol or to the corresponding hydrocarbon 
depends upon the proportions of BF.sub.3 and of the silicon hydride used 
in carrying out the reaction, as well as upon the reaction time. 
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
The invention will be readily understood by those skilled in the relevant 
art from the following Examples, which are descriptions of reactions that 
have been conducted, and are presented solely for the purpose of 
illustrating and disclosing, but not of limiting, the invention.

EXAMPLE 1 
An olefin believed to be E-2-undecene and n-undecane were produced from 
5.00 g. 2-undecanone dissolved in 10 ml. methylene chloride by reaction 
with BF.sub.3 gas in the presence of 11.24 g. triethylsilane. The reaction 
was conducted in a 100 ml. 3-neck flask to which was charged a 30 ml. 
portion of methylene chloride; thereafter the flask was fitted with a 
reflux condenser, a Claisen adapter with two addition funnels and a glass 
capillary which extended below the surface of the methylene chloride in 
the flask. The reflux condenser was cooled by a 2-propanol dry ice 
combination, and had a side tube exiting to a water trap. The 2-undecanone 
dissolved in methylene chloride was charged to one of the addition 
funnels, while the triethylsilane was charged to the other. An ice bath 
was placed around the reaction flask; stirring was commenced; and BF.sub.3 
gas was bubbled into the methylene chloride solution in the flask at a 
moderate rate sufficient that evolution of unreacted BF.sub.3 from the 
reaction mixture could be observed. The ketone solution of 2-undecanone 
was then added to the flask over a period of a few minutes, followed by 
the silane, which was added in 3 minutes. Stirring and passage of BF.sub.3 
into the solution were continued for one hour, after which time the flow 
of BF.sub.3 was stopped, and the reaction was quenched by addition of 
approximately 15 ml. saturated aqueous potassium carbonate solution to the 
reaction mixture. The organic material in the reaction mixture was 
extracted with diethyl ether, and the ether extract was washed with water, 
dried over sodium sulfate, and freed of volatile materials by means of a 
rotary evaporator at room temperature. The liquid which remained was 
purified by vacuum distillation at a temperature of 160.degree.* and a 
pressure of 0.5 torr. The final yield was 4.40 g. product analyzed by 
vapor phase chromatography, nuclear magnetic resonance and infrared 
spectroscopy, and found to consist of 83 percent n-undecane and 17 percent 
of an olefin believed to be E-2-undecane on the basis of its infra-red 
absorption at 960 cm.sup.-. The overall yield of the alkane, n-undecane, 
based upon the 2-undecanone charge, was 80 percent. 
FNT * All temperatures reported herein are in degrees C. 
The procedure described above, or a modification where the ice bath was not 
employed, but the reaction was conducted, instead, under ambient 
conditions of about 20.degree. C., has also been used to increase the 
hydrogen to carbon ratio of numerous other organic compounds. The 
compounds reacted, the number of equivalents, based upon compound reacted, 
of the triethylsilane, unless otherwise indicated, the reaction 
temperature, the reaction product, and yield data, for representative ones 
of these reactions are set forth in the following Table: 
TABLE 
__________________________________________________________________________ 
Reaction 
Silane Reaction 
Time Percent Yield of Product(s) 
Organic Compound Reduced 
Equivalents 
Temperature 
Minutes 
RCH(OH)R' 
RCH.sub.2 R' 
__________________________________________________________________________ 
Undecanal 1.5 0.degree. 
10 92 
Benzaldehyde 18 25.degree. 
11 52 
p-Methylbenzaldehyde 
7 25.degree. 
6 45 
p-Chlorobenzaldehyde 
9 25.degree. 
10 72 
p-Methoxybenzaldehyde 
2 25.degree. 
10 100 
p-Cyanobenzaldehyde 
3 25.degree. 
10 100 
p-Nitrobenzaldehyde 
1.5 25.degree. 
5 100 
Cyclohexanone 2 25.degree. 
1.5 82 
Cyclohexanone 4 25.degree. 
30 90 
2-Methylcyclohexanone 
2.2* 25.degree. 
60 88 
Adamantanone 8 25.degree. 
30 80 
p-Cyanoacetophenone 
3 25.degree. 
10 100 
p-Nitroacetophenone 
4 25.degree. 
3 100 
p-Nitroacetophenone 
4 25.degree. 
30 100 
Benzyl Alcohol 8 -70.degree. 
5 40 
2-Octanol 1.2 0.degree. 
75 58 
1-Adamantanol 1.3 25.degree. 
20 100 
2-Adamantanol 1.3 25.degree. 
15 98 
2-Phenyl-2-Pentanol 
1.1** -60.degree. 
5 82 
2-(p-Nitrophenyl)-2-butanol 
1.1*** 0.degree. 
15 100 
__________________________________________________________________________ 
*Dimethylethylsilane. 
**(R)-(+)-1-naphthylphenylmethylsilane. 
***Phenylneopentylmethylsilane. 
Fructose and cotton have also been reacted with BF.sub.3 in the presence of 
triethylsilane by substantially the procedure described in Example 1. In 
each case, the presence of hexane in the reaction product was established 
by gas chromotography. Such reaction has also been used to react 
1-naphthaldehyde and fluorenone to produce, respectively, 
1-methylnapthalene and fluorene, as well as to react stilbene oxide. 
It will be apparent from the data presented above that the instant 
invention provides a simple reaction by means of which the hydrogen:carbon 
ratio of various organic compounds, provided that they have functionality 
as set forth above, can be increased, and that the reaction conditions are 
not critical. For example, the reaction time has been conducted at 
temperatures ranging from -70.degree. to 25.degree., and it is believed 
that temperatures at least as high as 200.degree. would be operable. 
Similarly, while the reactions reported above have all been conducted at 
atmospheric pressure of substantially one bar, it is believed that either 
higher or lower pressures could be employed ranging, for example, up to 
about 1000 psi. The reaction of organic compounds having the ketone, 
aldehyde, hydroxyl and epoxide function has been specifically described. 
Compounds having the acetal the ketal, the hemiacetal and the hemiketal 
function all react in the presence of BF.sub.3 to form an aldehyde or 
ketone function and are, therefore, equivalent as starting materials. This 
is demonstrated by the identification of hexane when fructose and cotton 
were reacted with BF.sub.3 in the presence of triethylsilane by 
substantially the procedure described in Example 1. 
It will be apparent from the foregoing examples of silanes in the presence 
of which the reaction of the instant invention proceeds that any silicon 
hydride, i.e., any silicon compound having at least one hydrogen attached 
directly to silicon, can be used to cause the reaction to proceed. It is 
believed that the great affinity of silicon for fluorine is responsible 
for the general operability of silicon hydrides, and for the reason that 
this affinity enables them, in effect, to sequester fluorine from the 
BF.sub.3 reactant and consequently to release hydrogen for reaction with 
the organic compound. 
The data presented above indicate that the use of a comparatively long 
reaction time and a comparatively large number of silane equivalents 
favors the production of hydrocarbons, while the use of a comparatively 
short reaction time and of a comparatively lesser number of silane 
equivalents favors the termination of the reaction at an intermediate, 
e.g., alcohol, stage. Ordinarily, it is desirable to use at least one 
silane equivalent, based upon the organic compound, to enable complete 
reaction. On the other hand, there is usually no reason to use more than 
about ten silane equivalents, although, disregarding possible waste of 
silane raw material, a greater excess does not appear to be detrimental. 
Ordinarily, reaction proceeds as far as it is capable of proceeding in not 
more than about 60 minutes, and reaction is frequently complete in as few 
as ten minutes. Reaction times of at least about one minute are usually 
preferred. 
The reaction according to the invention should be carried out under such 
conditions of temperature and pressure that both the silicon hydride and 
the liquid in which the reaction is conducted exist in the liquid phase. 
This makes -95.degree. about the minimum temperature that can be employed 
when methylene chloride is the liquid (freezing point -96.7.degree.), and 
necessitates either the use of a liquid reaction medium which freezes at a 
temperature lower than methylene chloride or the use of superatmospheric 
pressure if silane (SiH.sub.4, boiling point -112.degree. at 760 
millimeters Hg pressure) is used as the silicon hydride. The best mode 
contemplated for practicing the method of the invention involves the use 
of superatmospheric pressure. For example, the organic compound to be 
reacted, e.g., cotton, the reaction liquid, e.g., methylene chloride, and 
a suitable catalyst,* e.g., palladium, can be charged to an autoclave 
lined with polytetrafluoroethylene and equipped with at least one valved 
inlet; after sealing of the autoclave with a cover, also lined with 
polytetrafluoroethylene, silane is introduced into the autoclave through 
the inlet to develop sufficient pressure within the autoclave to cause 
solution of the silane in the methylene chloride or the like. The reaction 
can be conducted at ambient temperature of about 25.degree., but elevated 
temperatures up to about 200.degree. can be employed, if desired, to 
increase the rate of reaction. Ordinarily, there is no point in removing 
heat from the system to lower the temperature thereof below about 
25.degree.. The amount of silane introduced into the autoclave can range 
from perhaps 0.01 to 0.1 equivalent, based upon the organic material 
charged. BF.sub.3 is then introduced into the autoclave, for example in an 
amount substantially equivalent to the previously charged silane. As 
reaction proceeds, silicon tetrafluoride is formed from the silane, and 
B.sub.2 O.sub.3 is formed from the boron trifluoride. This reaction causes 
a reduction in pressure within the autoclave, so that progress of the 
reaction can be monitored on the basis of autoclave pressure. When the 
pressure drops sufficiently to indicate substantial reaction of the silane 
and BF.sub.3, hydrogen is introduced into the autoclave; in the presence 
of the palladium or other suitable catalyst, hydrogen reacts with silicon 
tetrafluoride, forming silane and hydrogen fluoride; the latter reacts 
with the previously formed B.sub.2 O.sub.3, regenerating the BF.sub.3 
required to cause further reaction between the silane and the organic 
compound, which can again be monitored on the basis of pressure. Repeated 
additions of hydrogen can be made until reaction is indicated to be 
complete by the maintenance of a substantially constant pressure within 
the autoclave following a hydrogen addition. The autoclave can then be 
vented and opened, and the desired hydrocarbon recovered in a conventional 
manner, e.g. by filtration and distillation, from the other components of 
the reaction mixture for a subsequently described reaction. 
It will be apparent that various changes and modifications can be made from 
the specific details set forth herein without departing from the spirit 
and scope of the invention as defined in the appended claims.