close

Вход

Забыли?

вход по аккаунту

?

Cathodic Acylation of Aryl Olefins.

код для вставкиСкачать
Cathodic Acylation of Aryl
Procedure
Olefins[**]
cr-Methylstyrene(2.36g, 20mmol) and lithium perchlorate
(4.38 g, 40 mmol) are electrolyzed in anhydrous N,N-dimethylformamide (80ml) at - 10°C in a diaphragm cell at a platinum
mesh cathode (geometrical surface area 18 cm') at a current
density of ca. 25mA/cm2 until 20mF have passed through
the cell. The catholyte is added to a cold 80% solution of
hydrazine hydrate which has previously been acidified to pH
5 with conc. H2S04, and the mixture is heated to 130°C
for 2h. Bulb to bulb distillation (80-9OoC/0.1 torr) of the
residue after the usual workup gives pure 4-methyl-4-phenyl4,5-dihydropyridazine (1.48 g, 8.6 mmol) ['H-NMR (CDCI3):
6=1.5 (s, 3H), 4.5-4.65 (m, 1 H), 6.2-6.4 (m, 2H), 7.1-7.4
(m, 6H); MS (70eV): m/e=172 (M', 4%), 157 (M+-CH3,
100 %)I.
By Rainer Engels and Hans J. Schafer"]
Electrochemical reductive acylation has so far only been
accomplished with activated olefins such as a$-unsaturated
carboxylic esters and nitriles"'. We have now found that
aryl olefins can be cathodically acylated, and in particular
formylated (see Table 1).
Table 1. Products and yields of reductive acylation of aryl olefins.
Product (current eKiciency)
Aryl olefin [a]
Electrophile
a-Methylstyrene
4-Phenyl-2-pentanone
(68 %) [b]
2-Phenyl-4-heptanone
n-Butyronitrile
(SO %) [b, c]
i-Butyronitrile
2-Methyl-5-phenyl-3hexanone (54 %) [b]
Acetonitrile
4-Phenyl-2-butanone
(20 %) [d]
I ,4-Diphenylbutane
(48 %) [d]
N,N-Dimethylformamide 2-Methyl-2-phen ylsuccinaldehyde (86 %) [d, e l
(91 %) [d, e, h]
N,N-Dimethylformamide Phenylsuccinaldehyde
(82 %) [d,
2,5-Diphenyladipaldehyde (12 %) [d, f, g]
~
a-Methylstyrene
a-Methylstyrene
Styrene
a-Methylstyrene
Styrene
Acetonitrile
Received: March 13, 1978 [Z 964 IE]
German version: Angew. Chem. 90,483 (1978)
CAS Registry numbers:
Products listed in Table 1 (top to bottom): 17913-10-9; 59540-81-7;
66515-35-3; 2550-26-7; 1083-56-3; 66515-34-2; 66515-33-1; 6651 5-32-0;
a-methylstyrene, 98-83-9; styrene, 100-42-5; acetonitrile, 75-05-8; n-butyronitrile, 109-74-0; i-butyronitrile, 87-82-0; N,N-dimethylformamide, 68-12-2;
4-methyl-4-phenyl-4,5-dihydropyridazine,66551-66-4; 2,5-diphenyladipinaldehyde 0-methyl oxime, 6651 5-31-9
fl
[ 11 H. Lund, C. Degrand,Tetrahedron Lett. 1977,3593; 7:Shono, 1. Nishiguchi,
H.Ohmizu, J. Am. Chem. SOC.99, 7396 (1977).
[2] G . J . Hoijtink, J. v. Schooten, E . de Boer, W I . Aalbersberg, Recl. Trav.
[a] Electrolysis conditions: 20mmol of aryl olefin and 40mmol of LiC104
in 80mI of anhydrous electrophile, diaphragm cell, platinum mesh cathode,
current density ca. 10 to 30 mA/cm2, current passed 20 mF.
[b] Determined by gas chromatography (5 % SE 30 on Chromosorb W).
[c] 2-Methyl-2-phenyl-3-hexanone (3 %) was detected as by-product.
[d] Isolated yield.
[el Isolated as 4-methyl-4-phenyl-4,5-dihydropyridazine.
Isolated as 0-methyloxime derivative.
[g] Small amounts of 2-phenylpropanal appear as a further minor product.
[h] Reduction by lithium in N,N-dimethylformamide.
Chim. Pays-Bas 73, 355 (1954).
[3] E . A . Evans, J. Chem. SOC.1956, 4691.
[4] P. L. Pickard, 7: L. Tolbert, J. Org. Chem. 26,4886 (1961).
[fl
Synthesis of Donor-substituted Sulfonium Salts
The reduction of the aryl olefins Ph(R')(J=CHZ at the
cathode (directly or by deposited lithium) leads to radical
anions (1) and/or dianions (2)[" which can react by path
A or path B with the electrophilic solvent E.
R'
;C=CH,
Ph
I
T'
J?
+
+e
PhSSH,
PathA
Y o
Ph-C-CH,
o
R'
I
Ph-$-CHZ-E"
R' Eo
I
(1)
I+
By Hans-Ulrich W q n e r and Aviv Judelbaum"]
Despite their potential utility as synthetic intermediates,
sulfonium salts of type ( A ) or (B) stabilized by donor substit-
1'.
I
I
Ph-C-CH,
HzO/@
H
R'
I
7-O
Ph-q-CH,
A Ph- 8'
g- CH2-Eo
C=O
(5)
PathB
R' = H, Me
00
I
E = HCO-NMe,. R2-C=N; ( 3 ) : Eo = -CH-NMe,,
R2 = Me, n P r , iPr
The resulting anionized hemi-aminals (3)[31and ketimines
(4)L41 are subsequently hydrolyzed to the products ( 5 ) and
( 6 ) , respectively.
R2
I
( 4 ) : Eo = -C=No
uents have hitherto not been isolated"'. Only N-acyl derivatives of (B)['] and a cyclic salt of type ( A ) stabilized with
trifluoromethyl groups[3] have so far been described. Kresze
et a!. recently reported the synthesis of the related sulfonium
salts (C)I41.
p]
Prof. Dr. H. J. Schafer, Dip1.-Chem. R. Engels
Organiscb-chemisches Institut der Universitat
Orleans-Ring 23, D-4400 Munster (Germany)
I**] This work was supported by the Deutsche Forschungsgemeinschaft.
460
[*] Dr. H.-U. Wagner, Dipl.-Chem. A. Judelbaum
Institut fur Organische Cbemie der Universitat
Karlstr. 23, D-8000 Miinchen 2 (Germany)
Angew. Chem. int. Ed. Engi. 17 (1978)No. 6
Документ
Категория
Без категории
Просмотров
1
Размер файла
104 Кб
Теги
acylation, cathodic, olefin, aryl
1/--страниц
Пожаловаться на содержимое документа