Read
the disclaimer
All
references were first discovered in "The Journal of Forensic
Science",
Vol. 37, yr 1992, pp. 301-322
======================================
From
"Tetrathedron Letters", No 45, pp 3323-3326, yr 1964
"...
(R1-CH-OR)-P(+)-(C6H5)3 --{base}-->
(R1-C(+)-OR)-P(+)-(C6H5)3
--{R2-C=O-R3}--> R1C(OR)=C(R2)R3
--{H3O(+)}--> R1(C=O)CH(R2)R3
The
phosphonium salt (I, R=R1=CH3) was prepared by dissolving
triphenyl
phosphine
(76.4 g., 0.29 mol) and [alpha]-methyl ether [5] (28.4 g.,
0.30 mol) in
125 mL of benzene. After standing for 40 hrs. the
mixture
was filtered
and washed with ether giving a white solid (112 g., 88%
yield)
consisting of the crude phosphonium salt containing one molar
equivalient
of benzene crystallization. ... This salt is
slightly
hygroscopic
on exposure in air but can be stored indefinitely in a
sealed
container.
The ylid (II
R=R1=CH3) resulting from treatment of (I, R=R1=CH3) with
base was
found to be very unstable at room tempature, the
characteristic red color dissappearing within a few seconds.
Accordingly,
the preparation and reaction of this ylid was best carried
out at -40
C. The general procedure used for the preparation of the
crude enol
ethers (III, R=R1=CH3) was as follows: The phosphonium
salt
(33 mmol)
was suspended in 40 mL of glyme at -40 C under nitrogen.
Potassium
t-butoxide (33 mmol) in 15 mL of glyme was added with
stirring
over 5 minutes. At this point a solution of the aldehyde or
ketone (30
mmol) in 5 mL of glyme was added over five minutes. The
mixture was
allowed to warm to rrom tempature over one hour and was
then
directly distilled.
The
distillates obtained were usually quite pure samples of enol
ethers
in the
reaction of aldehydes. ...
...
The methyl
ketones were conveniently prepared from the enol ethers by
mixing with
one equivalent of water with 0.5% HCl and enough methanol
to effect
solution. The solution was heated to boiling and the
solvent
was then
evaporated to give relatively pure samples of the ketones in
practically
quantitive yields. ...
TABLE
I
Methyl
Ketones from Aldehydes and Ketones
Carbonyl
Compound / Methyl Ketone / Yield [6] /...
Benzaldehyde
/ 3-Phenyl-2-propanone / 88% /..."
=====================================
From "The
Journal of Organic Chemistry", Vol 54, yr 1989, page 733-4
"...
Scheme
II
R2-CH=C(R1)-NO2 --{2 H(+)/ CF3SO3H}--> ...
--{C6H6}-->
C6H5-CH(R2)-(C=O)-R1
...
TABLE
I
Nitro
olefin/ R1/ R2/ temp C/ time/ [alpha]-phenylmethyl ketone/
Yield
4a/ CH3/ H/
-40/ 1 min/ 6a/ 85%
...
In a typical
procedure, a solution of 2 nitropropene (4a) (300 mg) in
benzene
(total amount of benzene used was 30 equivalents) was added
to
a
well-stirred solution of TFSA (10 equiv with respect to 4a) and
benzene with
the co-solvent of methylene chloride cooled to -40 C in a
dry
ice-acetone bath. The reaction mixture was immediately (after 1
minute)
poured into large excess dry methanol (100 mL) cooled to -78
C
with
vigorous stirring [8]. After being warmed to the ambient
tempature
(10-15 min), the yellow solution was diluted with water
(150 mL),
nuetralized with powdered NaHCO3, and saturated with NaCl.
The solution
was extracted with CH2Cl2, dried over Na2SO4, and
concentrated, and the residuewas flash chromatographed (SiO2) to
give
pure
3-phenylpropan-2-one (6a) from nitro olefin (4) is demonstrated in
Table
I.
..."
==========================
Also there
is: "Journal of the American Chemical Society", Vol 93,
yr 1971, pp
524-526
It uses
acetate salts of Mg or Ce to add acetone to an olefin but it
does not
refer to benzene specificly, whereas the Forensic Science
article that
referenced it implied that you could just use Mg(OAc)2 and
benzene to
create P2P.
"As a
representive example, the reacton of acetone with octene-1 in
the
presence of
manganic acetate under a nitrogen atmosphere was studied
in detail. A
solution of ocetene-1 (7.5 mmol), acetone (200 mmol), and
manganic
acetate (15 mmol) in glacial acetic acid (40 mL) containing
10%
potassium acetate was heated at 85 until the brown manganic
color
had
dissappeared. Three major products were isolated after the
work
-up:
the saturated ketone ... (I, 1.13 mmol); an unsaturated ketone
.... (II,
0.54 mmol)... ; and a keto acetate ... (III, 1.78 mmol)..."
============================
