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Патент USA US3077504

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3,077,494
United States Patent ()?lice
2
1
be added thereto, the lithium metal reacts less vigorously
with the molten alcohols thereby preventing any uncon
3,077,494
FORMATION
trolled reactions.
ALKOXIDE CATAllrei‘o‘ FOR URETHANE
_
The alkoxides of liquid alcohols are readily prepared
by the addition of small pieces of freshly-cut alkali metal
James R. Gri?ith, 4201 53rd Ave, Bladensburg, Md.
No Drawing. Filed July 5, 196b, Ser. No. @0979
_
Patented Feb. 12, 1963
to thoroughly dried alcohols. In some instances it is
necessary to pulverize the alkali metal in order for the
3 Claims. (Cl. 2e(l—-47l)
reaction to proceed ‘satisfactorily.
(Granted under Title 35, US. Code (1952), sec. 266)
Caution should be
exercised because the reaction may tend to accelerate
The invention described herein may be manufactured
continuously until charring occurs. This acceleration can
and used by or for the Government of the United States 10 be avoided if the container is submerged in a cooling
of America for governmental purposes without the pay
medium. With higher molecular Weight alcohols, it is
ment of any royalties thereon or therefor.
This invention relates to urethane formation and, more
usually found necessary to warm the alcohol slightly to
initiate the reaction.
speci?cally, to catalytic method for forming urethanes by
The alkoxides of the solid alcohols which melt below
15
the reaction of tertiary alcohols with isocyanates.
70° C. are readily prepared by the direct addition of alkali
metal to the melt. Alcohols that melt between 70 and
While it is known to prepare carbamates (urethanes)
in sul?icient yields by reacting primary and secondary
120° C. will form alkoxides if the rates of hydrogen ‘evoluQ
alcohols with isocyanates at room temperature, applica
tion are carefully controlled. The alkoxides are more
tion of this same procedure to tertiary alcohols is not 20 di?icult to prepare, however, from alcohols having high
practical since yields of not more than about 10% of the
er melting points, for the alkali metal alkoxides are usual‘
desired carbamates are thereby obtained. The uncatalyzed
ly insoluble in the alcohol melts.
reaction of tertiary alcohols with isocyanates is for prac
The tertiary acohol urethanes contemplated by the pres*
tical purposes non-existent at room temperature, while at
ent invention comprise those which are derived from
elevated temperatures the reaction yields dehydration
products. There is therefore no satisfactory method for
25
isocyanates having the general formula:
preparing urethanes of tertiary alcohols comparable to
those for the primary and secondary alcohols. The sensi
in which R represents an aromatic or an aliphatic hydro
tivity of the carbinol center toward urethane formation
carbon radical; the tertiary alcohols represented by the
falls off’ rapidly as hydrogen atoms are replaced by hydro 30 general formula:
.
carbon groups, and the necessity for heating promotes the
formation of ureas and ole?ns along with small amounts
of urethanes. In fact, ole?ns are formed in such appreci
R3
able quantities that heretofore isocyanates have been
recommended as convenient dehydrating agents for terti
in which R1, R2 and R3 are also aromatic or aliphatic
hydrocarbon radicals, namely, alkyl, aryl, aralkyl or
ary alcohols.
It has now been discovered that relatively high yields
alkaryl groups may be of the saturated or unsaturated type
of urethanes of the tertiary alcohols may be obtained if
and in general the radicals may also have substituted
the esteri?cation is carried out in the presence of an
groups, suchas the halogens.
alkali metal alkoxide at room temperature, and the re 40
Tertiary alcohols which are not sterically laden with
action is both rapid and convenient in forming new
aryl groups about the tertiary carbon atom form urethanes
urethanes which have not been possible to produce by
more readily, although it is possible to form urethanes
previous methods. The addition of an alkali metal alkox
having a considerable number of aryl groups attached
ide has also been found useful for urethane formationof
secondary alcohols which generally require increased tem
peratures to react with the isocyanates.
.
The urethanes of this invention are prepared rapidly
thereto.
Illustrative examples of alcohols capable of
combining with an isocyanatc molecule are the saturated
aliphatics, e.g. Z-methyl-Z-propanol, 2-rnethyl-2-butanol,
Z-methyl-Z-pentanol, 3-methyl-3-pentanol, 3-ethyl-3-pen
and in sufficient yields by reacting tertiary alcohols and
secondary alcohols containing therein catalytic amounts
tanol, B-ethyl-B-nonanol, etc.; the unsaturated aliphatics,
of alkali metal alkoxides of lithium, sodium or potassium
metal with an isocyanate, for instance, phenyl isocyanate
or l-naphthyl isocyanate, until the reaction is substan
tially complete. The reaction is carried out very rapidly,
rnethyl-l-hexyn-S-ol, etc; cyclic type such as l-ethyl cyclo
hexanol; the aryl type, for instance, l,l-diphenylethanol,
1,1,2-tripl1enylethanol, etc. The isocyanates, by way of
example, are represented by the phenyl isocyanate and the
e.g. 3-methyl-l-butyn-3-ol, 3-methyl-l-pentyn-3-ol, 3,5-di
with or without a solvent, although the inclusion of a low
l-naphthyl isocyanate.
boiling solvent helps to keep the reaction mixture cool 55 The new tertiary alcohol urethanes formed by means
and thus avoids alcohol dehydration.
of the present invention are generally white, crystalline
In practising the invention, an alkoxide is introduced
solids, often of needle structure, soluble in most organic
into the tertiary alcohol, preferably by dissolving lithium,
solvents and insoluble in water. They are valuble com
sodium or potassium metal directly therein. The tertiary
pounds in the preparation of a variety of commercially
alcohol and the isocyanate are then reacted in equal molec 60 valuable chemical products. They are particularly use
ular proportion in the presence of the alkali metal alco
ful as weed killers: under greenhouse conditions many of
holates, but it is found desirable to have an excess of the
alcohol present to suppress a too-vigorous, exothermic side
reaction. Of the alkali metals, referred to above, lithium
the phenylcarbamates are active. At 1 1b./ acre the growth
of cereal seeds may be completely inhibited. At a con
centration of 500 ppm. the more active of these are
is more advantageous for this purpose, since lithium 65 herbicidal against quack grass.
alkoxides are generally more soluble in organic solvents
and dissolve in greater concentrations in the higher molec
ular weight alcohols than the corresponding sodium or
potassium salts. Lithium, moreover, is less active than
either sodium or potassium in reactions with active hy 70
drogen; consequently, in forming alkoxides with alcohols
which must be melted initially before the alkali metal can
Their chlorinated de
rivatives are also useful as insecticides. Urethanes in re
cent years have appeared promising in the ?ght against
leukemia and clinical studies are now in progress on many
of these compounds.
A few typical tertiary alcohol urethanes are given in
the following table, although these are understood to be
3,077,494
merely exemplary of the broad class of compounds as
described herein.
TABLE
Most of the solid tertiary alcohols are low-melting solids
and the lithium alkoxides may be prepared from the melt,
with proper precautions to avoid an uncontrolled reaction
during the alkoxide formation. It is generally advan
'
Carbamate of
tageous to prepare the alkoxides in fractional amounts
of the total alcohol and to add this catalytic solution in
increments to the urethane reaction.
Melting
.
Tertiary
Alcohol
Isocyanate
K-methyl-l-butyn-3-ol _______ __
2-methyl-2-pem annl
,
>
Phenyl isocyanate ________ __
_____(lo
Do ______________ _.» ...... ._
S-meth yl-l-pentyn-ii-cl
Phenyl isocyanate- _ . ._
i-ethynyl cydohexano
v1,l-diphenylethanol__._
Example III
130-131
52-53
l-Naphthyl isocyanate ____ __
‘3,-methyl-3—nonanol_____
Points,
° C.
'
1,1,2-triphenylethanol _______ __
135-136
10
91-92
166-167
39-40
144-145
170—17l
v‘:Th'e following examples are illustrative of this inven
tion: _
The dry alcohol, 2-methyl-3-butyn-2-ol, is divided into
a small portion, of about 3 grams, and a larger portion
of 54 g. (total 0.68 mole) which is placed in a three-neck
?ask ?tted with re?ux condenser, stirrer and separatory
funnel and dissolved in 100 ml. of dry ether. The smaller
portion is treated with a freshly-cut piece of lithium metal
about 0.2 of a gram and warmed to accelerate the evolu
tion of hydrogen. One-half of the dissolved catalyst is
'
Example I
added to the ?ask. While the solution is stirred rapidly,
' Into a 250 m1. three-necked ?ask ?tted with a re?ux
40.0 g. (0.34 mole) of phenyl isocyanate is added drop
placed 60.0 grams (0.68 mole) of tertiary amyl alcohol
‘keep the ether boiling gently. The remaining catalyst is
water. After the ethereal solution was dried over an
practiced otherwise than-as speci?cally described.
condenser, a stirring motor and an addition funnel was 20 Wise by way of the separatory funnel at such a rate as to
added in portions as needed. The ether is evaporated
which had been dried over calcium hydride. In the alco~
after completion of the reaction, and the urethane is ex
hol was dissolved 0.2 gram of lithium metal and then
100 ml. of ethyl ether, which had been dried over calcium 25 tracted and recrystallized from petroleum ether. The
yield of pure 2-methyl-3-butyn-2-N-phenyl carbamate is
hydride, was added to the ?ask. From the addition fun
64.8 g. (94%), MP. 130-l31° C.
nel 40.0 grams (0.34 mole) of phenyl isocyanate was
Obviously many modi?cations and variations of the
added dropwise or just rapidly enough to keep the solu
present invention are possible in the light of the above
tion boiling gently. Upon completion of the isocyanate
addition, the resulting solution was transferred to a separa 30 teachings. It is therefore to be understood that within
the scope of the appended claims the invention may be
tor'y funnel and extracted with ?ve 100-ml. portions of
hydrous calcium sulfate, the ether was removed by evap~
oration on a warm water bath, and the residue that re
What is claimed is:
1. In the method of preparing urethanes by the reac
tion of a tertiary alcohol with an isocyanate, the improve
mained was dissolved in 90 ml. of petroleum ether. The 35
ment which comprises conducting the reaction in the
solution was then cooled to room temperature and allowed
presence of an alkali metal alkoxide at a temperature in
to remain until the carbamate had precipitated. The pre
the range of about 20 to 30° C.
cipitated carbamate was removed by ?ltration, two-thirds
2. In the method of preparing urethanes by the reac
of the petroleum ether was removed by evaporation and
the ?ltrate was placed at —20° C. for 24 hours. The fol 40 tion of a tertiary alcohol with an isocyanate, the im
provement which comprises conducting the reaction in
lowing day additional precipitate had formed which was
the presence of lithium alkoxide at a temperature in the
removed by ?ltration and combined with that previously
range of about 20 to 30° C.
obtained. The combined precipitates were then recrystal
3. In the method of preparing urethanes by the reac
lized from petroleum ether to yield 56.0 grams (81%)
of pure'tertiary amyl N-phenylcarbamate, M.P. 42° C. 45 tion of a tertiary alcohol with an isocyanate, the im
provement which comprises adding an alkali metal alkox
Example II
ide'of said tertiary alcohol in small amounts sut?cient to
After 0.5 gram of lithium metal was dissolved in 85.0
grams (0.68 mole) of 3,5-dimethyl-l-hexyn-3-ol, 40.0
grams, (0.34) mole of phenyl isocyanate were added to 50
the alcohol dropwise over a period of 45 minutes while
the solution was stirred constantly. Upon complete addi
tion of the isocyanate, 100 m1. of petroleum ether (B.P.
100~120° C.) was added and the mixture was heated to
boiling. After 9 grams of an insoluble residue was re
moved by ?ltration, the ?ltrate was cooled overnight at
—-20° C. The next day 64 grams of crude carbamate
(urethane) was removed by ?ltration. This solid was re
catalyze said reaction at a temperature in the range
of about 20 to 30° C.
References Cited in the ?le of this patent
UNITED STATES PATENTS
2,860,166
Newcomer et a1 _______ __ Nov. 11, 1958
OTHER REFERENCES
Dieckrnann et al.: Ber. Deut. Chem, 37, 4627-38
( 1904).
Chabley: Beilstcin’s Handbuch (4th edition), volume
crystallized from 100 ml. of petroleum ether by cooling to
1, page 381 (1918).
—-20° C. to yield 45.5 grams (55%) of pure 3,5-dimethyl 60 Tarbell et al.: J our. Am. Chem. Soc., volume 64, pages
1-hexyn-3 N-phenylcarbamate, M.P. 77-78° C.
2229-2230 (1942).
‘
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