close

Вход

Забыли?

вход по аккаунту

?

N N-DichlorourethaneЧA Selective Chlorination Reagent; Synthesis of Corticoids.

код для вставкиСкачать
An X-ray structure analysisL31of the manganese complex
has now shown the isolated molecule to contain two octahedral
units joined by a shared edge (cf. Fig. 1).
The central moiety containing the Mn, N, and S atoms
is almost planar, while the MnzNz four-membered ring is
exactly planar, showing that the nitrogen atoms no longer
possess a stereochemically effective lone pair. All the Mn-N
distances are equal within the limits of error and somewhat
longer than would correspond to a single bond (based on
the covalent radius of 1.398, for MnoL4]).Both the Mn...Mn'
distance of 3.318(2)8, and the angle in the central portion
of the molecule show that no direct metal-metal bond is
present; the small N-Mn-N'
angle (76") even suggests a
repulsive interaction between the two Mn atoms.
The NSOFZgroup serving as bridge has a strongly distorted
tetrahedral symmetry. The S-0 and S-F bond lengths closely resemble those in other compounds R-NSOF,['].
The
very short N-S bond of 1.434(6) 8, corresponds to a bond
order of ca. 2.S6] and indicates strong d,-p, bonds between
sulfur and nitrogen; it is ca. 0.05 8, shorter than in CINSOFz[sal
and-within the limits of error-of the same length as in
(CO)sReNSOFz[5b1.The NSOFz groups of [Mn(C0)4NSOFz], can be formally regarded as four-electron donors
[cf. ( I a ) ] , and in the compounds R-NSOFz with R=C1
and Re(C0)5 as two-electron donors. However, the surprisingly large Re-N-S
angle of 140" in (CO)5ReNSOF2suggests a bonding contribution from the nitrogen lone pair;
in CINSOFz, on the other hand, the lone pair is fully effective
(Cl-N-S:
114")'sa1.
There are two possible ways of describing the bonding:
the manganese atoms have the oxidation number + 1 in (1 a)
and 0 in ( 1 b), the NSOF2 group being considered as a fouror three-electron donor. No decision in favor of either of
these two alternatives is possible on the basis of available
experimental evidence.
The bonds of the CO ligands correspond to those in other
carbonyl complexes[71;nevertheless, the trans effect (MnC,, = 1.807A, Mn-C,, = 1.8998,) is relatively pronounced.
[7] Cf., e.g., R . Bau, S. W Kirtley, 7: N . Sorrell, S . Winarko, J. Am. Chem.
SOC.96, 988 (1974); S. J . La Placa, W C. Hamilton, J . A. Ibers, A.
Davison, Inorg. Chem. 8 , 1928 (1969); references cited therein.
N,N-Dichlorourethane-A Selective Chlorination Reagent; Synthesis of Corticoids
By Yehuda Mazur and Zvi Cohen"]
Continuing our studies on the selective functionalization
of steroid molecules['], we searched for a simple method to
introduce a functional group at C I 1 in deoxycorticoids, to
replace the microbiological method commonly used for this
purpose.
We have now found that saturated steroids can be selectively
chlorinated with N,N-dichlorourethane (DCU).
DCU is a stable, distillable, but highly reactive pseudohalogen which is easily prepared by reacting urethane with chlorine[']. This compound was found by Ch~brieu'~]
to add to
olefins, giving the unstable N-chloro-N-(P-chloroalky1)carbamates, which can be readily reduced to the d-(P-chloroalky1)carbamates. We observed that cyclohexane on exposure to
light in the presence of DCU is converted into chlorocyclohexane and urethane and that benzene solutions of adamantane
and DCU on irradiation with a sunlamp gave t-chloroadamantane in high yields. Reaction of DCU with steroids resulted
mainly in chlorination at C-9: androstane-3P,17P-diyl diacetate was converted into a mixture of tertiary chlorides, which
after dehydrochlorination with AgC104 gave the corresponding 9(11)- and 14-androstene derivatives in 40 and 9 % yield,
re~pectively[~I.
In the case of steroids with dihydroxyacetone
side chains, DCU proved to be even more selective. We have
chosen (1 a ) and ( 2 a ) as starting compounds; these compounds are intermediates in the preparation of the medically
useful 16a- and 16P-methyl~orticoids['~.
LOAC
Received: September 26, 1977;
revised: February 6, 1978 [Z 929 IE]
German version: Angew. Chem. 90, 287 (1978)
CAS Registry numbers:
[Mn(CO)dNSOF,] 2r 659 15-49-3
_____
[l] R. Mews, 0. Glemser, J. Chem. SOC.Chem. Commun. 1973, 823.
[2] L. F . Dahl, C. H . Wei, Acta Crystallogr. 16, 611 (1963).
[3] 1050 independent diffractometer data, solution by conventional methods,
refined with anisotropic temperature factors to R=7.1 %; space group
P2,/n (standard formulation P2,/c-C:,,, No. 14), Z = 2; lattice constants
(20°C): a=1002.4(5), b=1175.1(5), c=736.8(4)pm, ,9=100.96(4)",
d,,,, =2.08, d,,, =2.1Og
[4] F. A. Cotron, D . C. Richardson, Inorg. Chem. 5 , 1851 (1966).
[5] a) H . Oberhammer, 0.Glemser, H . Kliiuer, Z. Naturforsch. A 2 9 , 901
(1974); b) B. Buss, D. Altena, to be published.
[6] 0 . Glemser, A. Miiller, D. Bohler, B. Krebs, Z . Anorg. Allg. Chem. 357,
184 (1968).
Angew. Chem. lnt. E d . Engl. 17 ( 1 9 7 8 ) No. 4
[*] Prof. Dr. Yehuda Mazur, Zvi Cohen
Department of Organic Chemistry, The Weizmann Institute of Science
Rehovot (Israel)
281
The diacetate ( I a ) [ ' ] was irradiated in the presence of
DCU in benzene and then dehydrochlorinated with AgC104;
the only product was the corresponding 9(11)-pregnenederivative (1 b ) (yield 41 %). For the synthesis of the 9a-fluoro-16Pmethylcorticoid ( 2 d ) , the acetate ( 2 a)[51was converted into
the bis(trifluoroacetate) ( 2 b)[41, which was then treated with
DCU, and finally with AgC104. Subsequent hydrolysis of
the trifluoroacetyl groups with NaN3 in methanolr61andoxidation with pyridinium chlorochromate afforded the known
~ ~%"yield
~ based on ( Z b ) ] , which is easily
ketone ( 2 ~ ) [55
converted into the glucocorticoid ( 2 d ) [ 7 b 1 .
There is a close analogy between the halogenation reactions
with DCU and those with iodobenzenedichloride['J: both reactions proceed by a free radical chain mechanism involving
photochemically generated chlorine atoms. These chlorine
atoms serve as hydrogen abstracting radicals, as seen by comparing the reactivity of the tertiary and the primary hydrogens
in 2,3-dimethylbutane. In chlorinations with DCU this ratio
was found to be 89: 1 in CSz, 50: 1 in benzene and 9: 1
in the absence of a solvent while the respective ratios for
reactions with chlorine at comparable temperatures and concentrations as found by Russell[91were 109: 1, 49: 1 and 4: 1.
N-Monochlorourethane, which occurs as intermediate, can
also serve as a chlorination reagent, however it is much less
effective than DCU.
Procedure
Synthesis of (1 b). A solution of (I a) (1 g, 2.04mmol) and
DCU (0.65g, 4.12 mmol) in dry benzene (150ml) flushed with
Nz was irradiated with a 160W-sunlamp for 10h in an atmosThe reaction mixture was washed with NaHS03,
phere of Nz.
dried, and evaporated to dryness. The residue was dissolved
in acetone (150ml) and treated with an aqueous solution
of AgC104 (6g in 60ml). The precipitate formed was filtered
off, the solvent evaporated and the residue extracted with
ether and washed with water. Subsequent column chromatography (dry S O z , CH2Cl2)afforded ( I b ) (0.41g, 41 %), m. p.
138--139"C, [aID= -IS", 'H-NMR (CDCI,): 6=0.95 and
5.32 (H at C-19 and C-9).
Organic Syntheses Using Sheet Silicate Intercalates:
Low-temperature Conversion of Olefins to Secondary
Ethers[**]
By John M . Adams, James A. Ballantine, Samuel H . Graham,
Richard J . Laub, J . Howard Purnell, Paul I . Reid, Wafa I:
M . Shaman, and John M . Thomas"]
We have discovered that a range of cation-exchanged montmorillonites will smoothly convert I-alkenes (1) to the corresponding secondary ethers ( 2 ) when hexane solutions of the
olefin are refluxed in presence of the solid montmorillonite
for 5-10h.
2RCH=CH2
(1)
(a), R
Hz 0
= n-C4H9;
R H C -C H3
I
P
RHC-CH,
( b ) , R = n-CSH,I;
CAS Registry numbers:
( I a ) , 65899-44-7; (I b ) , 65899-43-6; ( 2 a ) , 21670-48-4; ( 2 b ) , 65899-45-8;
( Z C ) , 13852-68-1; / 2 d ) , 378-44-9; DCU, 13698-16-3
[l] I-' Mazur, Pure Appl. Chem. 41, 145 (1975); Z. Cohen, E. Keinan, I!
Mazur, A. Ulman, J. Org. Chem. 41, 2651 (1976); and references cited
therein.
[2] ?: A . Foglia, D. Swern, J. Org. Chem. 31, 3625 (1966); 33, 766 (1967).
[3] P. Chabrier, Fr. Pat. 56285 (1952).
[4] All the new compounds were characterized by 'H-NMR-, 13C-NMRand mass spectra.
[5] We thank Dr. H. Herzog (Schering Co., Bloomfield, N. J.) for supplying
samples of ( l a ) and ( 2 a ) . Cf. E. P . Oliveto, R. Rauser, L . Weber, A .
L . Nussbaum, W Gebert, C . 7: Coniglio, E. B. Hershberg, S. Tolksdorf,
M . Eider, P . L. Perlman, M . M. Pechet, J. Am. Chem. SOC.80, 4431
(1958).
[6] L . Weber, E. L . Shapiro, L . E . Finckenor, H . L. Herzog, US-Pat. 3383394
( 1 968).
[7] a) J. A . Attenburrow, J . E. Connet, W Graham, J. F . Oughton, A . C .
Richie, P. Wilkinson, J. Chem. SOC.1961, 4547; b) 7: R . Carrington,
S . Eardley, J . Elks, S. F. H . Green, G . I . Gregory, A . G . Long, J . C .
P . Sly, ibid. 1961, 4560.
[8] R. Breslow, R . J . Corcoran, J. A . Dale, S. Liu, P. Kalicky, J. Am. Chem.
Soc. 96, 1973 (1974); R. Breslow, R. J. Corcoran, B. B. Snider, ibid.
96, 6791 (1974); R. Breslow, B. B. Snider, R. J . Corcoran, ibid. 96, 6792
(1974).
[9] G . A. Russell, J. Am. Chem. SOC.80, 4987 (1958).
282
Ic), R
= n-CsHl3
GLC, mass spectrometry and the 'H-NMR spectrum established the identity of the product. It cannot be efficiently
produced by any other known preparative method. Chromatographic separation of the diastereoisomers was possible.
A range of definitive experiments['] demonstrated that the
source of the ether oxygen was the interlamellar water (hydration sphere of inorganic cation) and that reaction takes place
in the interlamellar region, there being an optimal water content for a given cation of the original sheet silicate (see Fig.
1).
0
50
100
f
Received: February 2, 1978 [Z 931 IE]
German version: Angew. Chem. 90,289 (1978)
(2)
-
150
[hl
200
Fig. 1. Yield of ether (expressed as percentage consumption of interlamellar
water) as a function of time for clays with (a) one layer (b) two layers
and (c) three layers of water between the aluminosilicate sheets. 0.5g clay
was used in each case with 5 g hex-1-ene.
The montmorillonite principally used in the work had a
cation-exchange capacity of 66 mequiv/l00g of air-dry aluminosilicate, but tests on montmorillonites from a number
of different sources showed that all were effective for the
conversion ( 2 ) + ( 2 ) . In the preliminary experiments described here, a considerable excess of alkene over aluminosilicate was employed. Yields of up to 65 %, based on consumed
['I
Prof. J. M. Thomas ['I. Dr. J. M. Adams, Dr. S. H. Graham, P. I.
Reid
Edward Davies Chemical Laboratories, University College of Wales
Aberystwyth SY23 1NE (UK)
Prof. J. H. Purnell, Dr. J. A. Ballantine, Dr. R. J. Laub, W. Y. M.
Shaman
Department of Chemistry, University College of Swansea
Singleton Park, Swansea Sa2 8PP (UK)
['I Present address: Department of Physical Chemistry, University Chemical
Laboratories, Lensfield Road, Cambridge CB2 EP (UK)
[**I Work supported by the Science Research Council
Angew. Chem. Int. Ed. Engl. 17 (I 978) NO. 4
Документ
Категория
Без категории
Просмотров
0
Размер файла
230 Кб
Теги
synthesis, reagents, selective, chlorination, corticoid, dichlorourethaneчa
1/--страниц
Пожаловаться на содержимое документа