ACYL IODIDES IN THE REACTION
295
acetyl iodide, led only to the corresponding
α
ꢀdikeꢀ
For C19H24 anal. calcd. (%): C, 90.47; H, 9.52.
tone PhCOCOPh with mp 95°C (lit.: mp 95–96°C
[6]).
Found (%): C, 89.99; H, 9.96.
1
IR (
ν
, cm⎯ ):
ν
(CO) is absent, 3020–2820 (
(ring C–H)).
, ppm): 0.89 (t, 3H, CH3CH2, 3J
6.91 Hz), 1.39 (m, 2H, CH3CH2), 1.47 (quin, 2H,
CH3CH2CH2
3J = 6.91 Hz), 2.15 (dt, 2H, CH2CH,
ν
(C–
H)), 1600, 1500 (ring C–C), 720, 690 (
δ
The observed difference in the photochemical
behavior of acetyl and benzoyl iodides seems to result
1H NMR (
δ
=
from steric factors and easier recombination of the
•
,
benzoyl radical PhC
O owing to its higher stability as
•
3J = 7.55, 3J = 7.68 Hz), 2.42 (s, 6H, CH3), 3.96 (t,
J J =
1H, CHCH2, 3 = 7.68 Hz), 7.20, 7.26 (d, 4H, Ar, 3
compared with the MeC
O
radical.
The process of acylation of aromatic ring was found
to be a sole reaction direction upon photolysis of trimꢀ
ethylacetyl and valeroyl iodides RCOI (R =nꢀBu, tertꢀ
Bu) in toluene medium. The photochemical reaction
of toluene with valeroyl iodide and pivaloyl iodide
begins with acylation of the phenyl group. However,
aryl alkyl ketones RCOC6H4Me formed at this stage
proved to be only intermediates in the studied photoꢀ
chemical processes.
7.94 Hz).
13C NMR (
δ
, ppm): 14.08 (CH3CH2), 21.04
CH3Ar), 22.82 (CH3CH2), 30.40 (CH3CH2CH2),
35.65 (CH3CH2CH2CH2), 50.65 (CH), 127.76 (Cꢀ2,6
arom.), 129.13 ( ꢀ3,5 arom.), 135.39 (Cꢀ1–CH),
142.76 (C4–CH3).
(
C
The mechanism of formation of 1,1ꢀbis(4ꢀmethꢀ
ylphenyl)pentane includes the addition of toluene,
which behaves as a hydrogen donor in photochemical
processes, to the carbonyl group of nꢀbutyl 4ꢀmethꢀ
ylphenyl ketone, a product of toluene acylation at the
In particular, the photolysis of valeroyl iodide
ꢀBuCOI in toluene leads to 1,1ꢀbis(4ꢀmethylpheꢀ
nyl)pentane, bp 165°C, n2D0 1.5445, as a main reaction
n
para position of benzene ring, followed by reduction of
product (decaneꢀ5,6ꢀdione was detected in trace resulting 1,1ꢀbis(4ꢀmethylphenyl)pentanol with
amounts), Eq. 4. evolved hydrogen iodide.
nꢀBuCOI
n
+ I
nꢀBuCOCOBuꢀn +2I2
hν
nꢀBuCOI
Me
Me
Me
hν, C6H5Me
C6H5Me
–HI
hν
(4)
+ H2O + I2.
+ 2HI
OH
nn
nn
nn
HC Buꢀ
C Buꢀ
C Buꢀ
O
Me
Me
It is well known that ketones readily undergo phoꢀ
tochemical reduction in the presence of hydrogen
donors, and this reaction provides a basis for the preꢀ
parative synthesis of pinacols, for example, benzopiꢀ
nacol [7].
m
ꢀMe), 7.14, 7.32 (d, 2H, 3
J
= 8.32 Hz, Ar), 7.02, 7.23
(m, 4H, Ar).
13C NMR (
δ
, ppm): 21.61 (Me, ), 31.38 (Me3C),
A
34.25 (Me
4), 148.11 (Cꢀ1), 20.76 (Me3,
(Me ), 122.23 (Cꢀ6), 126.02 (Cꢀ2), 126.11 (Cꢀ4),
C), 125.09 (Cꢀ2), 128.70 (Cꢀ3), 134.73 (Cꢀ
B), 31.35 (Me3C), 34.48
Photolysis of pivaloyl iodide tertꢀBuCOI in toluene
medium led to a mixture of 3ꢀ and 4ꢀ(tertꢀbutyl)methꢀ
C
127.92 (Cꢀ5), 137.36 (Cꢀ3), 151.03 (Cꢀ1).
ylbenzenes (
Eq. (5).
A
and B) in 1.5 : 1 ratio (total yield 45%),
The mechanism of formation of isomers
A
and B
1
IR (
ν
, cm⎯ ): 3960–2860 (
ν
(C–H)), 1600, 1480,
(ring C–H)).
includes cleavage under the action of UV irradiation
(the Norrishꢀtype I cleavage [8, 9]) of isomeric 3ꢀ and
4ꢀmethylphenyl tertꢀbutyl ketones, products of photoꢀ
chemical acylation of toluene with pivaloyl iodide tert
α
1460 (ring C–C), 800, 760, 700 (
1H NMR (
9H,
δ
δ
, ppm): 1.35 (s, 9H, ꢀMe3C), 1.353 (s,
p
ꢀ
mꢀ
Me3C), 2.35 (s, 3H, ꢀMe), 2.39 (s, 3H,
p
BuCOI formed at the first stage of the process.
DOKLADY CHEMISTRY Vol. 435
Part 1
2010