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endo-Hydroxytrioxatris--homotropilidenes.

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C 0 MMUNICATIONS
tone)], should prefer a twisted conformation'5' (Br, 3-OR
quasiequatorial, 4-OR quasiaxial) in which the center of the
C C double bond is effectively shielded on the @-sideby
213-H.
Br
Br
Br
endo-Hydroxytrioxatris-a-homotropilidenesI*
'J
X
X
( a ) , X = Br, R = 13
( b ) , X = Br, R = A c
(c), X = C1, R = H
i d ) , X = C1, R = A c
By Horsi Prinzbuch, Christoph Riicker, and Huns Fritz'*]
Interesting aspects of the chemistry of trisheterotris-o-homobenzenes (1) include the thermal [,,2,+ ,,2,+ ,,2,] cycloreversion to trisheteronins["'] and the regio- and stereoselective
ring cleavage to give biologically important aminohexitoIsllhl.Preparation of similar target molecules-such as potentially "trishomobenzenoid" carbenium ions of type (2)
(X = 0, NR), aminoheptitols-requires
specifically endosubstituted trisheterotris-o-homotropilidenes
(3) (X = 0, NR;
'
Br
\
I
151
\
X
(a), R
(b), R
= H
= Ac
Y = OR, Y' = H). We have developed preparatively useful
syntheses for two (cis; a,a,p) of the three isomeric trioxa
compounds la,2a,4~t,5a,7a,9cu- and 1 0 ( , 2 ~ ~ , 4 ~ ~ , 5 @ , 7 @ , 9 0 The advantage of using (56) as a precursor of (8u) is that
3.6,10-trioxatetracyclo[7.1.0.02~4.05~7]decan-8~-ol
[(Ka) and
the
site of OH addition on reaction with HOX is immaterial
( I f a ) ]l" which
comprise the
reaction sequences
(C-5,
C-6) as long as it occurs from the side of the epoxide
(46)+(56)+ (6c)+ (7c)+(Su) and ( 4 b ) - + ( 5 ~ ) + ( l O a ) + ( l l a ) ~ ~ ~ .
ring (i. e. from the f3 side); double ring closure always leads
The starting material (4b)[,I is readily accessible from tropexclusively to (8). Since vicinal trans-diaxial H/X systems
ilidene; under controlled conditions i n the presence of the
are absent, olefin formation cannot compete. Only unsatisweakly nucleophilic base diazabicyclononene (DBN) (THF.
factory regio- and stereoselectivities are obtained on addition
20 "C. 15 h), HBr elimination proceeds without competition,
of HOBr [NBS, acetone/water ( l : l ) , 5OoC, 24 h]: never
in contrast to the reaction involving, e. g., sodium methoxmore
than 10% of ( 6 4 (isolated as (66); m.p. 173 " C (CCI,);
ide/methanol. According to 'H-NMR analysis [(CDCI,);
plane of symmetry evidenced by 'H- and "C-NMR spectra;
Ji.2=6.5. J 2 . 7 ~ 8 . 5 , J3.4=4.5. J4.5=5, J5.6=10.5, J6,7<3,
Jl.*( J b . 7 ) ~ 7J2.3
r (JS.h)=ll, J1.,(J4.5)=2.5 Hz) together with
Jl.7=4.5 Hz] the diacetate (5b) [m.p. 83 "C (CCI,), isolated
two epoxide cleavage products (HZO,HBr). In contrast, addiquantitatively]. as well as the diol (Za) [m.p. 113°C (acetion of HOCl is almost specific [tert-butyl hypochlorite, water/acetone (1 : I), 50 "C, 8 h]: subsequent hydrolysis affords
['I Prol. Ilr. H. Prin/.bach [ ' 1. Lhpl.-Chem. Ch Rucker. Prol. Dr. H . Frit7
90-95% (6c) [m.p. 170°C (subl.); (6d): m.p. 163°C (aceLehntuhl fur Organixhe Chrrnie der UnivrrsitZt
= J(,.,= 7.5, Jz.3= JS.h
= 1 1 , J1.4
=J4.5= 2.5,
tone/CCI,); J,.*
Albert\tras\e 21. 0-7XOO Freiburg (Germany)
J1.,=4.5 Hz] and 2-5% of the C1, addition product of the
[**I This work was supported hy the Deutsche Forschungsgemeinschalt and the
same configuration. The price paid for the high yield of (6c)
Fonds d r r Chcmischen Induhtrie. Ch. Ruchrr thanks the Studienstlftung des
Deutachcn Volkcs for a scholarship.
is a considerable drawback in the next stage. As expected,
[ ' ] To u honi correqpondence should he addres\ed.
only the transformation into (7c) proceeds readily in the case
An,cen: C hwn. In,. Ed. Engl. IX (1970) No. 8
0 Verlag Chemre, GmhH, 6940 Weinheim, 1979
05 70-0833/ 7Y/OXOX- 06 I I $ 02.SO/O
611
of (6c) [>90%, m.p. 127°C (methanol/CCI,); ( 7 4 : m.p.
145°C (CCI,/CHCI,); J i , l %, l , J 2 . 4 ~ 4 ,J 4 . 5 I~, J i (,=4.5,
J(,.7= 8, J7.x
= 7, J,, = 4.5 Hz]. During the long time required
for elimination of HC1 (24 h) the product uniformity is lost:
for example, after complete reaction with KOH/methanol
(20 "C, 24 h) only 30-35% of (#a) is obtained [m.p. 207 "C
(subl.); (86); m.p. 197°C (subl.); 'H-NMR (CDCI,. 360
MHz): 6=5.65 (t. 8-H), 3.44 (m, 2-, 4-H), 3.34 (m. 1-. 5-. 7-,
9-H), 2.21 (s, OCH,); J7.8 (J,..))= 1 Hz; "C-NMR (CDCII):
6 = 170.3 (CO), 67.0 (C-8), 58.7 (C-7. -9), 52.3 (C-1, -5). 48.2
(C-2, -41, 20.9 (CH,)]; products resulting from substitution at
C-2, C-4 and transannular ether formation arise preferentially["'. The yield rises to the fairly respectable value of 4550% of (#a) [42-48% based on (46)l-with similar by-products-on use of the reagent sodium glycolate/THF which
has proved of value in similar cases1']: only nonspecific decomposition occurs with DBN.
The critical step en route from (5b) to ( l l a ) is epoxidation:
the diacetate (5b) is resistant to m-chloroperbenzoic acid (in
C2H4Cl2) between 25 and 80°C. The diol (50) is also oxidized very slowly (3 d. 20°C) yet with an expectedly high
trans-selectivity; polymeric material is accompanied by 45%
of (1Oa) [m. p. 175 "C (ethyl acetate/benzene); (lob): m. p.
119- 120 'C (CCI,); J 2 . 4 = 4, JI.5 = 7, J,,, = 4.5. J(,.7 = 9, J7.s = 8
Hz] and traces of (7u) [m. p. 115 " C (ethyl acetate/benzene);
1, J,.,=8,
~
J7,=6.5, J,,,=4.5 Hz]. Nor
JI,2=1.5,J 2 . 4 = 4 rJ 4 . 5
could the early initiation of decomposition and secondary
reactions be delayed by variation of the reaction conditions
(peracid, temperature, buffer). No (fOa) is formed with
CF,C03H/Na2HP04 (CHLCL,20 "C). Epoxide ring closure
(IOa)+(lla) is fast and practically uniform [85-90'%; 3640% based on (Sb), m.p. 93-94°C (acetone/CCI,); ( I l b ) :
m.p. 85 "C (CCI4/pentane); 'H-NMR (CDCl,, 360 MHz):
6=4.90 (d. 8-H). 3.59 (dd, 1-H), 3.35-3.45 (m. 4-, 5-H). 3.30
(d, 9-H), 3.20 (dt, 2-H), 3.16 (dt. 7-H), 2.21 (s, OCH,);
Ji,z=3, J,,,=4.5. J2,4=3, J4,5=0, J 5 . 7 ~ 5 .J,.,=5.5, J , , = O
Hz: "C-NMR (CDCI3): 6= 170.4 (CO), 73.2 (C-8). 57.5, 55.8
(C-7, -9), 51.9, 50.8, 49.2, 48.6 (C-1, -2, -4, -5)].
The alternative of first converting (5a) into (%-the conformation having quasi-trans-diaxial OH/Br substituents is
readily accessible-and epoxidizing the product is less favorable. Although (Ya) is formed quantitatively under standard
conditions [m. p. 93-94 " C (ethyl acetate/benzene); (Yh):
m. p. 108-109 "C (CCI,)], its epoxidation is even slower and
more complex than that of (5a) and, moreover, non-stereoselective [ca. 5-10% of each (#a) and (lla)]lsl.
Compounds (5)-(14) are fully characterized by elemental
analysis and spectral data (MS, IR, 'H- and "C-NMR), and
the stereochemistry of the end products (8) and (11) is chemically confirmed, e. g. by oxidation to the tropone trioxides
and by comparison with the exo/endo a1cohols"l formed
from the latter compounds.
Received. June 21. 1978 [Z 39 IE]
German ~ e r s i o n Angew.
:
Chem. 91, 646 (1979)
Publication delayed at author\' request
CAS Registry numbers:
(4h). 59Y92-03-9: (JuJ. 67598-52-1: (5hJ. 67598-53-2: ( 6 ~ ) 67598-54-1.
.
Ihh).
67598.554
67s9x-s6-s,
h 7 s ~ n - s 7 - 6 :(7u). 67598-5x-7: ( 7 ~ ) 6
. 7s~~-598 , (7d). 67598-60-1: (Xu), 67598-61-2: IXh). 67598-62-3: IOuJ. 67598-63-4: ( Y h j .
67598-64-5; ( / O n ) . 67650-77-5: //ObJ, 6759X-65.6. ( 1 / u ) . 67650-78-6: ( 1 l h J .
67650-79-7
m).
m).
[I] a) H. Prmzhach. R. Srhwe>inger. M Breunrn,yer. R. Gullenhump. D. HunkIer.
Angew. Chem. 87. 349 (1975); Angew. Cheni. Int. Ed. Engl 14. 347 lIY75),
and references cited therein; b) cf.. c s.. the synthesis of atreplamine fro111 ci\bensene trioxidc. R. Schnw~ingcr.H. Prmihuch. rhid 87. 625 (19751 and 14.
630 (tY75). respectively.
612
0 Veriag
Chemie, GmbH, 6940 Weinherm. 1 Y 7 Y
[2] The third isomeric alcohol ( & < t )
/12) has been o b t a n e d Irrtni ~ [ 3 . ~ t i w
pone triohide: tI Pr;n:bui/i. W. Scppcli. / I Frrr:. t o he p u h l i ~ l i c ~ l
131 Attenipted radical halogenation o f the CHI group i n ~i.s-tropilidrnrtrioride
141 led only to suhstitution in the epaxide ring.;: ('h. R u d w . Di\\srtati(in.
Universitat Freiburg 1979.
[4] H. Prin:bo</i, ( I . Rucker. Angew. Chem. W. 61 I ( I Y 7 6 ) ~A n g e w Chem Int.
Ed Cngl. 15. 5.59 ( lY76).
IS] W. T o d i i t ~ r m a nFortschr.
~,
Chem. tvrsch 1.7. 37X (1970).
[h] I.ther\ and chloride\ 0 1 type f1.i) and 114). X=OCH,. CI. could he irolatt.d
and characteriLed.
171 R. Schwe$mgcv, H. Prin:buch. Angew. Chem 84. 9YO (lY7?): 4 n g e w Chem.
Int. t d Engl / / . 942 (lY72).
[XI The hitherto unknown ris-2.3:4.5-tropone dioxide ( m p. XX C. 44-60"L:
JI,=3.J1,=4.J~,.=1.8.
J~,,=12. J i . = 3 5 . J , , = 4 H 7 ) c a n heuhtainedi'ra
/ciu), e.,q hy oxidation with RuOd ( R u 0 2 . 2 equiv NalO,. CHCI,/H:O.
20 C )
Hexamethyldisilane/Iodine: Convenient In Situ Generation of Iodotrimethylsilane['*]
By George A. Uiah, Suhhash C. Narang, B. G. Balurum Gupta, and Ripudaman Ma1hotra"l
lodotrimethylsilanel" has recently found extensive use in
organic syntheses. Because of the relative difficulty of preparation and its hydrolytic and photoinstability, emphasis was
placed on continued work on the in situ generation of the
reagent. Work in this area has resulted in the use of phenyltrimethylsilane/iodine"',
allyltrimethylsilane/iodine, and
3,6-bis(trimethylsilyl)-l.4-cyclohexadiene/iodinereagents''!
These reagents, however, can either produce undesirable byproducts or involve tedious syntheses of starting materials.
Recently, chlorotrimethylsilane/sodium iodide was also introduced as an iodotrimethylsilane equivalent, but its utility
is confined to the essential use of acetonitrile as solvent[41.
We now wish to report the use of hexamethyldisilane/iodine [(2)/12] as an extremely effective and mild in situ iodotrimethylsilane reagent giving no by-products. This reagent can
be advantageously used for the mild cleavage of esters (/),
carbamates (5). ethers (3), and sulfoxides. Alcohols can be
equally well transformed into corresponding alkyl iodides
with the reagent.
Esters ( I ) are cleaved to the corresponding acids in very
high yield. The reaction was applied with equal ease to methyl, ethyl, and benzyl esters of aliphatic and aromatic carboxylic acids.
RC02R'
I Me.SiSiMe* /2)/12
2 H,O
RCO,H
+ R'I
Aliphatic ethers (3) can be cleaved to the corresponding
alcohols or further transformed into alkyl iodides by varying
the reaction conditions. When cyclohexyl methyl ether (3d)
was reacted with HMDS/12 reagent in chloroform solution at
[ * ] Prof. Dr. G . A. Olah, S . C . Narang, B. G. B. Gupta. R. Malhotra
Hydrocarbon Research Institute. Department ot Chemistry
University of Southern Calitbrnia
University Park. Los Angeles. Calilbmia YO007 ( U S A )
[**IPart 74 i n the Series Synthetic Methods and Keactions. Support lor this
work hy the National Science Foundation and the National Institute\ 01 Health
is gratelull? acknowledged. Part 73 ( L A Oluh. 'l D. VmAnr. M Art.unwhi.
Tetrahedron Lett, in press.
i)S70-0833/ 79/0808-0612 $ 02.S0/0
Angeu. Chem. Inl. Ed. Lngl 1 8 f / Y i Y / No. N
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