close

Вход

Забыли?

вход по аккаунту

?

Mixed Carboxylic-Dichlorophosphoric AnhydridesЧReactive Intermediates in Acyl Chloride Synthesis with POCl3.

код для вставкиСкачать
The p-CD cavity is filled by 6.5 water molecules distributed
statistically over eight sites (Fig. 1). The remaining 5.5 water
molecules of the dodecahydrate are spread over eight sites
between p-CD molecules. Because no water hydrogen atoms
could be located, the assignment of hydrogen bonds must
be based on distance criteria. One of the O...O distances,
(OW5...OW8,2,32A)indicates that both sitescannot beoccupied simultaneously. All otherO...O contacts between oxygen
atoms within the cavity (2.6A to 3.0A) satisfy the generally
accepted distance criteria, The OW2.. .0(4)3distance of 2.98 A
may possibly indicate the first observed hydrogen bond to
glycosidic oxygen in saccharideocrystal structures. All other
OW.. .0 ( 4 ) contacts exceed 3.3 A.
The water molecules near O(2), O(3), and near the 0(6)
rims are also in contact with hydroxyl groups of adjacent
p-CD molecules, establishing a hydrophilic surface of the
p-CD. water complex. The usual tetrahedral arrangement of
hydrogen bonding donor and acceptor groups around water
molecules is only verified for O w l , with O...OWI ... 0 angles
in the range 91” to 141” deviating significantly from the ideal
107”. Tetrahedra around OW2 and OW4 are even more distorted and OW3 has only three neighbors at suitable distances.
The remaining four water sites within the cavity have five
neighbors each, with O . . . O W . . . O angles from 50” to 166”.
In the “empty”r-CD. 6 HzO,two water molecules are located
within the ~ a v i t y [ ~They
~ - ~ lare
. at fixed, fully occupied positions and hydrogen bonded with each other and with two
O(6)hydroxyl groups. The r - C D ring is strongly deformed
by rotation of one glucose unit into a nearly vertical position
relative to the other five, and the ring of O(2)...0(3) hydrogen
bonds is disrupted. In all other complexes, the r - C D molecule
is “round” and the ring of 0(2)...0(3) hydrogen bonds is
fully established. This conformational change between “empty”
and “full” a-CD has led to the proposal of an “induced fit”-like
mechanism[5h1.
The larger p-CD molecule exists in p-CD. 1 2 H 2 0 in a
“ r o u n d structure and no conformational change except rotation of C ( 6 k 0 ( 6 ) bonds is observed upon complex formation
with other guests. Thus an “induced fit” type mechanism
can be ruled out for 0-CD.
Hence we infer that the driving force of complex formation
is provided mainly by hydrophobic forces and by van der
Waals interactions between guest molecules and the interior
of the p-CD cavity. “Activated water” may also come into
play because the coordination of the water molecules
entrapped within the p-CD cavity is by no means “ideal”
and some hydrogen bonding energy might be gained by expulsion of these water molecules. Further, entropy terms will
be appreciable if the eight water molecules are expelled.
Received: July 10, 1978 [Z 45 IE]
German version: Aiigew. Chem. 90, 738 (1978)
CAS Registry number:
P-Cyclodextrin dodecahydrate, 20986-1 9-0
~
~~~
[I]
[2]
[3]
[4]
[S]
[6]
171
[S]
M . L. Bender. M . Komiyama: Cyclodextrin Chemistry. Springer, Berlin
1978.
F. Cramrr, W Suenger, H.-Ch. Spatz, J. Am. Chem. Soc. 89, 14 (1967).
M. Komiyama, M . L. Bender, J. Am. Chem. Soc. 100, 2259 (1978).
I . Tahushi, Y I. Kiyosuke, 7: Sugirnoto. K. Yamamura, J. Am. Chem.
Soc. 100, 916 (1978).
a) W Saenger, Jerusalem Symp. Quantum Chem. Biochem. 8, 265 (1976);
b) W Saenger, M . Noltetneyer, P . C . Manor, B. Hingerty, B. Klar, Bioorg.
Chem. 5, 187 (1976).
J . S q t l i , Z s . Budai, Acta Chim. Acad. Sci. Hung. 94, 383 (1977).
J . A . Hamilton, M . N . Subesan, L. K. SteinrauJ A. Geddes, Biochem.
Biophys. Res. Commun. 73,659(1976); J . M . MacLennan, M . M. Harding,
IV. Eur. Cryst. Meeting, Oxford 1977, Abstr. PI1 28; J . J . Stezowski,
K . H. Jogun, E. Eckle, personal communication.
P. C. Manor, W Saenqer. Nature (London) 237, 392 (1972); J. Am.
Chem. Soc. Y6, 3630 (1974).
Angew. Chem. I n t . Ed. Engl. 17 (1978) N o . 9
Mixed Carboxylic-Dichlorophosphoric AnhydridesReactive Intermediates in Acyl Chloride Synthesis with
POC13 [**I
By Franz Effenberger, Gerd Konig, and Herbert Klenkc*j
The intermediacy of mixed anhydrides ( 3 ) , X = CI, has been
proposed“] in the preparation of acyl chlorides from salts
of carboxylic acids and phosphoryl chloride. Acyl dichlorophosphates have likewise been advanced as the actual acylating
agents in the “phosphoryl chloride method” developed by
7%. Wieland et al. for the acylation of amino acids“]. That
no such intermediates ( 3 ) have yet been isolated o r directly
identified, is probably due to instantaneous reaction of the
mixed anhydrides with nucleophiles still present in the mixture
(carboxylate) or being formed in the course of the reaction
(chloride).
We have now succeeded in preparing compounds ( 3 ) by
reaction of carboxylic anhydrides ( 1 ) with dichloro- (2 a)
or difluorophosphoric anhydride (2 b). They are characterized
by definite boiling points and correct elemental analyses; their
structure is confirmed by 31P- and 13C-NMR spectra [e.g.
( 3 a ) : 31P-(85 % HJP04,ext.) 6 = 1.66; I3C-NMR (CDCI,)
benzoyl carbon 6 = 158.3, 2Jo-c -o-p= - 1 1.5 Hz].
In the case of anhydrides containing aliphatic acyl moieties,
e. y. (3 e) and ( 3 ~ 7secondary
,
processes such as ketene formation or condensation reactions prevent product isolation ;however, these compounds can be prepared in dichloromethane
solution. The NMR spectra provide unequivocal proof of
both the presence and the structure of compounds (3).
+
(I)
(Za), X = C 1
(Zb), X = F
2 [R--c=O@ PO,X,~]
(4)
R
X
C6H5
C~HS
P-CH~C~H~
P-CH~C~H~
CH3
CHS
CI
F
Yield [”/.I
B. p . [“C/torr]
~-
(30)
(3b)
(3ci
(3d)
(3e)
(3f)
_ ~ _
.
c1
F
c1
F
61
80
60
7s
.=60 [a]
-90 [a]
7711052!10-*
97,’1054110
’
-
-.
[a] Determined spectroscopically in CH2CI2solution
Neither 31P-nor I3C-NMR shows any evidence of dissociation
of the anhydrides (3) into acylium ions ( 4 ) which might
be expected from the high leaving tendency of the dihalophosphate anion[31.The IR spectrum also displays only a C=O
vibration at 1780cm- and no band at higher frequencies
that could be attributed to stretching of the acylium function.
As expected, the anhydrides ( 3 ) are highly reactive. Unlike
the corresponding acyl chlorides, they form esters of tertiary
alcohols under mild conditions [e. g. ( 5 ) , 68 %] ; with arenes,
aryl ketones are produced without any Friedel-Crafts catalyst
[e.g. (6) and (7), 73 % (93 : 7)].
~.
~
[*I
Prof. Dr. F. Effenberger, Dip].-Chem. G. Konlg, Dr. H. Klenk
Institut fur Organische Chemie der Universitit
Pfaffenwaldring 55, D-7000 Stuttgart 80 (Germany)
[**I This work was supported by the Fonds der Chemischen Industrie.
695
0
0
@OCH3
+
As we were able to establish by 31P-NMR and by chemical
reactions, the formation of acyl chlorides from carboxylic
acids and POC13 proceeds via acyl dichlorophosphates (3).
When benzoic acid, triethylamine, and POC13 are reacted
in dichloromethane/ether at - 65"C, triethylammonium hydrochloride is precipitated. The presence of ( 3 a ) in the filtrate
is demonstrated by the 31P-NMR spectrum which remains
unchanged upon admixture of authentic ( 3 a ) .
If the solution is warmed to 6 0 T , benzoyl chloride and
benzoic anhydride are formed; addition of alkali chlorides
increases the percentage of acyl chloride. Apart from these
two compounds, tert-butyl benzoate (5) is formed in the
presence of tert-butanol at room temperature; benzoyl fluoride
is produced upon addition of sodium fluoride and catalytic
amounts of crown ether. Under these conditions, neither benzoyl chloride nor benzoic anhydride react with tert-butanol
or NaF. Leaving group in each case is the dichlorophosphate
ion, Cl,P(0)Oe.
+
R-C;
POCl,
+
K . Sasse in: Methoden der organischen Chemie (Houben-Weyl), 4th
Edit. Vol. 12/2, p. 556. Thieme, Stuttgart 1964
7%. Wieland, K . H. Shin, B. Heinke, Chem. Ber. 91, 483 (1958); N .
F . Albertson, Org. React. 12, 270 (1964).
C. Stol:er, A . Simon, Chem. Ber. 96, 288,453 ( 1 963); E. Fluck, E. Beuerle,
Z . Anorg. Allg. Chem. 411, 125 (1975); Z . Arnold, A. Holy, Collect.
Czech. Chem. Commun. 27, 2886 (1962); G. Martin, M . Marrin. Bull.
SOC.Chim. Fr. 1963, 1637.
H.Grunze, Z. Anorg. Allg. Chem. 324, 1 (1963).
Novel Mode of Formation of cis,tvans-l,5-Cyclooctadiene[**]
By Hans-Dieter Martin, Bernd Heiser, and Michael Kunze[*l
Highly strained, trans-configurated double bonds in eightmembered rings are usually generated by elimination['"], olefin
electrocyclic ring-opening["J, cycIoreversion[ld1,
or thermolysis['el. Previously, the cis,trans-isomerization of
cis-configurated double bonds has been used as photochemical
method[? We report here on photochemical and thermal fragmentations of the cyclic azo compound
which lead
in partly satisfactory yields to cis,trans-I ,5-cyclooctadiene (5).
131
AI
lCal
NEt3
R-C'<
0-C ( CH3)3 (5)
OH
CHzClz/
- 65 '\kO
0
60 "C
'
/
/
*
lGbl
0
1
llcl
//0
+ HNEt3ClQ +R X ,
C1
+N$T
R-C,
//O
F
The above evidence definitely establishes the acyl dichlorophosphates (3) as true intermediates in the acyl chloride
synthesis with P 0 C l 3; at the same time, the high acylating
potential of the mixed anhydrides (3) is demonstrated.
Procedure
Synthesis of ( 3 a ) : ( 2 ~ (9.80g,
) ~ 38.8
~ ~mmol) and benzoic
anhydride ( I ) , R=C6H5, (8.78 g, 38.8 mmol), are heated to
95 "C for 8 h, with strict exclusion of moisture. Fractional
distillation of the reaction mixture yields 1.7 g (17 %) of ( 2 a ) ,
b. p. 30"C/10-3 torr, and 11.3g (61 %) of (3 a), b. p. 77"C/10-3
torr.
Received: July 7, 1978 [Z 46 IE]
German version: Angew Chem. 90, 740 (1978)
CAS Registry numbers:
( I ) (R = C,H5),93-97-0;(Za), 13498-14-1 ;( Z b ) , 14456-60-1 ; f 3 a ) , 67598-46-3;
(3b), 67598-47-4; ( 3 c ) , 67598-48-5; ( 3 d ) , 67598-49-6; f3e). 67598-50-9;
(3f), 67598-51-0; (S), 774-65-2; f6), 611-94-9; ( 7 1 , 2553-04-0; tert-butyl
alcohol, 75-65-0
696
A detailed study of ( 1 ) was promoted by the previous
finding that (5) is a major product of the thermally induced
valence isomerization of the tricyclooctanes (2) and (3)[Ie1;
a diradicaloid ( 4 ) was postulated as product-determining
intermediate having three possible conformations ( 4 a)-(4 c)
fulfilling all the necessary geometrical requisites for stereoelectronically favorable cleavage. A consequence of this hypothesis
was the search for further suitable precursors for ( 4 ) and
thus also for (5). From the preparative standpoint the fragmentation of 7,8-diazatricyclo[4.2.2.0z~5]dec-7-ene (1 )
appeared the most suitable
As expected, irradiation of (1 ) (I,,, = 384 nm, E = 164) in
pentane does in fact afford (5) as main product. In
the yield of (5) is considerably lower (see Table 1).
On separation of the products slight losses are incurred
on account of the high sensitivity of (5). Compound (5)
was converted directly in the photolyzate with hexachlorocyclopentadiene.
Thermolysis of the tricyclic compound (2) under conditions
(A) likewise leads to (5) as a major product. Under conditions
[*] Prof. Dr. H.-D. Martin, B. Heiser, DipLChem. M. Kunze
Institut fur Organische Chemie der Universitat
Am Hubland, D-8700 Wiirzburg (Germany)
[**I Part 28 of the series "Small Rings". This work was supported by the
Deutsche Forschungsgemeinschaft, the Fonds der Chemischen Industrie, and
BASF AG.-Part 27: H . - D . Martin, R . Iden, H.J. Schiwek, Tetrahedron Lett.
1978, 3337.
Angew. Chem. Int. Ed. Engl. 17 (1978) N o . 9
Документ
Категория
Без категории
Просмотров
0
Размер файла
237 Кб
Теги
synthesis, dichlorophosphorsure, intermediate, carboxylic, pocl, anhydridesчreactive, mixed, chloride, acyl
1/--страниц
Пожаловаться на содержимое документа