close

Вход

Забыли?

вход по аккаунту

?

Crown Ether-Assisted Change of Regioselectivity in the Reductive Cleavage of Allylsulfonamides.

код для вставкиСкачать
Crown Ether-Assisted Change of Regioselectivity
in the Reductive Cleavage of Allylsulfonamides
In the second case, the observed effect can be explained
by increased polarization of the 0-Na bond in the probable key disodium intermediate (5) (or in the corresponding
intimate ion pairs). It was, therefore, reasonable to expect
that the yield of nerol (3) would increase due to the additional ionization of the polarized C-Na and 0-Na cbonds in such an intermediate (or in the corresponding intimate ion pairs). This could arise by introducing into the
reaction sphere a macrocyclic polyether capable of complexing Nae ionsr6'. As expected, reduction of (2) with Na
in NH, at -70°C in the presence of dibenzo-[l8]crown-6
(DBl8C6) (molar ratio 1 : 8 :O.l) gives, with a reproducible
yield of -75%, nerol (3) containing no more than 40/0 of
isogeraniol (4).
The above result may be interpreted in terms of preferential &protonation of the free ion pairs (6) specifically
solvated by participation of the polyether. Of the two mesomeric forms (7) and (8). (7) is favored due to the better
separation of the negative charge"'.
By Alexander M. Moiseenkou, Eugeni V. Polunin, and
AIexei V. Semenousky[*l
The widely used two-step carbon chain elongation reaction in isoprenoids via alkylation of a sulfur-stabilized ally1
anion has the main disadvantage that both during the alkylation"' as well as during the subsequent reductive desulfur i ~ a t i o n [ ' .procedures
~~
formation of double bond isomers
is possible. Although the regioselectivity of such alkylations ( a us. y) has been frequently studied, little attention
has been directed toward improving this step at the desulfurization stage.
We discuss here one of the possible approaches towards
solving this problem, exemplified by the reductive desulfonylation of nerylsulfonamide (2). The latter was found to
be the only (a)-prenylation product derived from the hydroxysulfonamide ( I ) (as its dilithium salt) which we have
8 Na/NH,,- 70°C
DB18C6,;.
DB18C6
Na
75%
>
'
1
recently proposed for the C5-homologation of isopreThus, the crown ether-assisted regiospecific reductive
noidsI4'.
desulfonylation opens up the possibility of employing the
hydroxysulfonamide ( I ) as an effective cisoid isoprenoid
Reduction of (2) under a variety of conditions such as
with amalgams, electrochemically, or with dissolving mesynthon for the stereospecific construction of polyprenols.
tals in amines, results in a mixture of nerol(3), isogeraniol
Using this procedure, we have recently successfully syn(4)13.41, and CLo-hydrocarbons,the whole process being
thesized (22, 62, lOZ, 14E. 18E)-farnesylfarnesol.
highly selective with respect to isogeraniol(4). Hence, with
Li in NH3 in the presence of tBuOH (molar ratio 1 :4 :1) at
Exverimenta I
-7O"C, the regioisomers (3) and (4).are formed in the'raTo a solution of Na (370 mg, 16 mmol) in NH, (50 mL)
tio 7 :93 in 70% yield. Reaction with Na in NH3 at - 70 "C
containing DBI8C7 (72 mg, 0.2 mmol) at -70°C under Ar
under these conditions gives (3) :(4) = 15 :85. In order to
was added a solution of (2) (605 mg, 2 mmol) in THF over
avoid the unwanted hydrogenolysis process the known
5 min with constant stirring. After an additional 2 min, the
mode of conversion of the alcohol into its a l c o h ~ l a t e [ ~ , ~ ~
excess Na was decomposed with NH4CI, NH3 evaporated
(with nBuLi in the molar ratio 1 :2 in tetrahydrofuran
off, and the residue treated with water and extracted with
(THF) at 0°C) was tried. In this case, however, although
hexane. The usual work-up gave 290 mg of product which
the yield of the alcohols did not enhance markedly, the rewas chromatographed on silica gel (30 8). Gradient elulative portion of isogeraniol (4) was found to be substantion, hexane-ether (up to 50 vol.% of ether) yielded 230
tially diminished in favor of nerol (3). Thus, reduction of
mg (75%) (3), b.p.= 105"C/10 torr, contaminated with 2the alcoholate of (2) with Li in NH, at -70°C gave (3) and
4% (4).
(4) in the ratio 30 :70. Pretreatment of (2) with NaH (1 :1)
Received: May 5, 1980 [Z 921 IEl
German version: Angew. Chem. 93. 1122 (1981)
and subsequent reaction with Na in NH3 at -70°C led to
CAS Registry numbers:
a similar result.
(2). 74323-42-5; (3). 106-25-2; (4). 16750-94-0; DB18C6, 14187-32-7.
I*]
Prof. Dr. A. V. Semenovsky (deceased), Dr. A. M. Moiseenkov [ 1' ,
Dipl.-Chem. E. V. Polunin
N. D. Zelinsky Institute of Organic Chemistry,
USSR Academy of Sciences
Leninsky Prosp. 47, Moscow 117913 (USSR)
1'1 Author to whom correspondence should be addressed.
Angew. Chem. Inr. Ed. Engl. 20 (1981)
No. 12
[I1 J . F. Biellmann, J . B. Ducep. Tetrahedron27, 5861 (1971); P. M . Arlani. J.
F. Biellmann, S . Dube. J. J. Vicens. Tetrahedron Lett. 1974. 2665; J. Hartmann. R. Muthukrishnan. M. Schlosser, Helv. Chim. Aaa 57.2261 (1974);
T. Nakai, H. Shiono, M. Okawara. Tetrahedron Lett. 1975, 4027.
(21 J . E. Baldwin, R . E. Hackler. D. P. Kelly, J. Am. Chem. SOC. 90. 4758
(1968); E. E. van Tamelen, R. A . Holton, R. E. Hapla, W . E. Konz. ibid.
0 Verlag Chemie GmbH. 6940 Weinheim, 1981
0570-0833/81/1212-10S7 S O2.S0/0
1057
94, 8228 (1972); K . Narasaka, M. Hayashi, T. Mukajyama. Chem. Lett.
1972. 259; P. A . Grieco. Y. Masaki, J. Org. Chem. 39, 2135 (1974); M. Kodama. Y. Marsuki, S. 110, Tetrahedron Lett. 1975, 3065; 1976. 1121; D.
Sauoia. C. Trombini. A . Umani-Ronchi, J. Chem. SOC. Perkin Trans. I
1977. 123; M . Kodama. S. Yokoo. H. Yarnada. S. 110. Tetrahedron Lett.
1978. 3121.
[3] M. Julia. D. Uguen, A . Callipoliris. Bull. SOC.Chim. Fr. 1976, 519.
141 A. M. Moiseenkou, E. V. Polunin. A . V. Semenousky, Tetrahedron Lett.
1979. 4759.
[5] K. Mori. M. Ohki. M. Matsui. Tetrahedron 30, 715 (1974); T. Karo. H .
Takayanagi, T. Uyehara, Y. Kitahara, Chem. Lett. 1977. 1009.
161 N. S . Poonia. A. V. Bajaj. Chem. Rev. 79. 389 (1979).
171 G. L. Olson. H.-C. Cheung. K . D . Morgan, C. Neukom. G . Saucy. J. Org.
Chem. 41. 3287 (1976).
[8] A. M. Moiseenkou. E. V. Polunin. A . V. Semenovsky. Tetrahedron Lett.
1981, 3309.
The Dihydrocorphinol- Corrin Ring Contraction:
A Potentially Biomimetic Mode of Formation of
the Corrin Structure'..]
By Vittorio Rasetti, Kurt Hilpert, Alexander Fassler,
Andreas waltz, and Albert Eschenmoser"'
Recently we reported"] the synthesis of the octahydroporphinoid (dihydrocorphinoid) metal complexes ( l a ) and
(Ib), their thermal rearrangements to the 19-acetylcorrin
complexes (3a) and (3b). respectively (''dihydrocorphinolL21
+ corrin ring contraction"), and the deacylation of (3a) by
hydroxide ions to give the nickel(rr) nonamethylcorrinate
(4a). These transformations point to a possible mechanism
for the formation of the characteristic corrinoid (A-D)
ring connection in vitamin B,2 biosynthesis. The corphinoid structure ( I ) of the starting material for the ring contraction was inspired by the structure of "Factor III''[31;
the latter is the most advanced intermediate in corrin biosynthesis to be isolated to date. The ring contraction
(1)-+(3) is closely related, both structurally and mechanistically, to our l-methylidene-1,19-secocorrin-corrin cycloi~omerization~~~,
especially to the non-photochemical
(A- D)-cyclization of a 1-methylidene-19-formyl-l,l9-secocorrin reported in 1977[4'.s1. The earlier conditions necessary for the conversions ( l a ,b)-(3a, b) (melting at 295"
and 260", respectively) were unsatisfactory with regard to
the intended role of the reaction as a potentiallyr61biomimetic model. We now describe further properties and variants of the reaction, among which are conditions that permit the ring contraction to proceed even at room temperature.
Scheme I. Summary of the reaction conditions (RT= room temperature). All compounds were isolated crystalline and characterized spectroscopially (UV/
VIS, IR, 'H- and "C-NMR, MS). For experimental details: K. Hilperf, Dissertation, ETH Ziirich (in preparation).
~~~~
~
Reactions
Reaction conditions and yields
lla)-/3a)
iib)-(3~
(3a)-(W
(1c) -12c)
cf. [I]
cf. [I]
cf. [I]
evacuated tube, in the dark, 220°C (70 s), yield 33%. apart from 28% educt and 13% (5a), isolated as Ni complex; or: visible hv (150 Watt)
in CH2CI,+CF,COOH (7. IO-"M), 40°C. yield 500/0
CF3COOH, Ni(OAc)2.4H20 in CH,CN, RT, yield 88%
CH3COOH/(C2H5),N (4: 1) in toluene, IOO"C, 2 h, evacuated tube, yield 90% [a]
hv visible (150 Watt) in benzene/CH2CI2 ( 6 :1) (degassed), 25"C, yield 75% [b]
CF,COOH/CH,CN (1 :100). O"C, 30 min, argon, in the dark, 62Y0(3d) + 20% educt
a) CF,COOH/CH,CN (1 :lo), RT, 16 h in the dark; b) Ni(OAc)2.4H20/NaOAc, RT, 3 h, yield 81%
(2c)-(2al
(2a)-(3a)
1-7~)
-(W
( 3 ~ ) - ( 3 4[cl
/3c)--12al
[a] In the 19-formyl model series [&I, the analogous ring closure occurs within hours at room temperature (cf. A. pfolrz, Dissertation ETH No. 6184, Juris-Verlag Ziirich 1978, p. 167). [b](3c) was isolated crystalline as the chlorozinc(ll) complex (m.p. =23O"C). [c] 19-Acetyl-1,2,2,7,7,12,12,17,17-nonamethylcomnium
perchlorate, orange crystals, M.p.= 139"C.-UV/VIS (C2H,0H): A,.,,=263 (log&-4.47), 292 sh (4.22), 307 sh (4.41), 321 (4.53). 371 (3.72). 392 sh (3.56), 458
sh (3.76), 488 sh (4.06), 512 (4.10) nm.-'H-NMR (CDC1,/300 MHz): 9 CHI singlets between 6 = 1.02 and 1.46, 1.99 (CH,CO), 1.88/2.65 (AB/J= 14/2 H-18).
1.8/2 H-13). 2.83/2.87 (AB/J= 19/2 H-8), 5.43 (t/J= U/H-15). 5.63/5.64 (2 s/H-5 and H-lo),
2.92/3.11 (AB/J= l9/2 H-3), 2.89/2.91 (ABX/JAB=19; laxI1.86/13.17 (2 s br., 2 NH) (J in Hz).-")C-NMR (CDCI,, 75 MHz): 6 = 19.5-29.2 (8 q/lO CH,), 42.6-52.0 (4 t/4 CH2), 43.2-52.2 (4 s/C-2,7,12,17), 78.8
(dC-1). 91.1 (dC-191, 91.4-93.3 (3 d/3 CH), 155.8-193.5 (6 ~ / >C-N),
6
210.8 (s/-).
[*I Prof. Dr. A. Eschenmoser, Dr. V. Rasetti,
dipl. Ing. Chem. ETH K. Hilpert, dipl. Naturwiss. ETH A. Fassler,
Dr. A. Pfaltz
Laboratorium fur Organische Chemie
Eidgenbssische Technische Hochschule, ETH-Zentrum
Universitststrasse 16, CH-8092 Ziirich (Switzerland)
[**I This work was supported by the Schweizerischer Nationalfonds zur FBrderung der wissenschaftlichen Forschung. Dr. E. Zass is thanked for assistance in completing the manuscript.
1058
0 Verlag Chemie GmbH, 6940 Weinheim. 1981
Melting the metal-free ligand (Id) (as the crystalline trifluoroacetate, m.p.=194"C) for one minute in an evacuated tube at 215°C did not lead to ring-contraction. Instead, ring-opening occurred (evidently followed by skeletal rearrangement) to give the ligand system of (54,which
was isolated as the crystalline nickel(r1) complex. The same
occurred with (Id) in pure trifluoroacetic acid (TFA) at
80°C in 1 h (though the reaction was not observed even
057~0833/81/1212-10S8$02.50/0
Angew. Chem. Int Ed. Engl. 20 (1982) No. I2
Документ
Категория
Без категории
Просмотров
0
Размер файла
227 Кб
Теги
crown, assisted, cleavage, ethers, change, reductive, regioselectivity, allylsulfonamides
1/--страниц
Пожаловаться на содержимое документа