close

Вход

Забыли?

вход по аккаунту

?

Cyclic Carbodiimides in Nitrene Rearrangements.

код для вставкиСкачать
J Threle. Liebigs A n n Chem 306. 142 (1899).J. 7hrc/r. K Trschbeor. t' Lus
(ow. rbrd I / ' ? 180 (1901). F W. Srhueler. C' Hunno. J Am Chem Soc 7.1.
3S28 (1951). R filler. E. J. Prasek. H A Lerpuld. Org Synth 43. 3 (19631
181 T h r t:-configiirdtioii of (50; was demonstrated by A Muquezrrau. Y . I o n HuI.-
1.11
erbrke. R. N Muller. Bull Sol: Chim Belg A;. 259 (1974).The E-configura
tron of r5d-A is demonstrated by a relatively large coupling of cu 0 7 Hz bctween the CH, group and the eiocyclic proton. € g lor /?el the ' H NMK
spectrum in (IDCI, shows a n A B X , sy\tem lor the methylidene proton ( A ) .
the ring proton H-4 (H). and the methyl group at C - 5 ( X ) ) : A = 2 18 ( X d . 6 24
(B). 7 21 ( A ) . J 4 u = O Y . J A x = 0 7 . J U x = 1.2 Hz (based on computer simulation and spin decoupling experiments1 The remainin?, signdls i n O r ) wrrr at
S = 3 . 8 4 ( \ . 3t((OCH,)).69?(d.J=R8Hz.ZH(arom)).:49(d.J=8XH1.
2H (arom ))
[9] T L. Gdchrrsr. U P Prur.von. J . Chem Soc. Perkin I I Y 7 6 . Y89.
* ::
Cyclic Carbodiimides in Nitrene Rearrangements["]
By Curt Wentrup, Celestin Thetar, Enrico Tagliaferri, Hans
Jorg Lindner, Brigitte Kitschke, Hans- Wilhelm Winter.
and Hans Peter Reisenauerl'l
Dedicated to Professor R o y Huisgen on the occasion of
his 60th birthday
In the course of our studies on the rearrangements of heterocyclic nitrenes it became necessary to postulate cyclic carbodiimides as key intermediates in some reactions['I. However, no such intermediate had ever been directly observed. We
now wish to report conclusive chemical evidence as well as
the direct spectroscopic observation of a cyclic carbodiimide
in reactions of this type.
The tetrazololl .S-c]quinazoline (1) exists exclusively as a
tetrazole in the solid state1'', but sublimation of (I) at
100 "C/10 . 4 torr and subsequent condensation of the vapor
on a KBr disc at - 196 " C afforded the azide (Z), characterized by intense IK absorptions at 2150, 2120, 1620, 1570, and
1370 c m - ' . The solid azide was transformed back into the tetrazole (I) on warming to ca. - 40 "C. It can thus be asserted
that a gas-phase thermolysis of (I) will give initially the a i d e
(2)!4!.
Flash vacuum thermolysis of (1) at temperatures above
torr gave 2-phenylbenzimidazole-1-carbonitrile
300 "C/lO
(8) in quantitative yield'5]. The same product was obtained in
92% yield together with 8% of indol0[2,3-b]quinoxalinc~'~
(10) by thermolysis of tetrazolo[ 1,5-a]quinoxaline (3) at
38OoC/10- torr. In the case of (3). only weak bands due to
the corresponding azide were observable by IR spectroscopy
at -. 196 " C , following thermolyses near the temperature
where the reaction (3)+ (8) takes place (300--400 "C).
['I
Prof Dr C Wentrup [ '1. Dip1 -Chem k 1 -W Winter
Fachbcreich Chemie dcr Univrrsilat
Hans-Mcerwein-Strasie. D-3550 Marburg (Germany)
Dr. C Thetaz. Dipl. Chem. E Tagliaferri
Insttrut d e Chimie Organiquc de I'llniversite
CH-I005 Lausanne (Switzerland)
Prof Dr. H. J Lindner. B. Krtschke
Institut fur Organischc Chemie der Tcchnischcn Hochschule
D-6100 Ihrmstadt (Germany)
Dr H. P. Reiscnauer. Institut fu: Organische Chemic drr Ilniversitat
DdWO Gicssen (Germany)
I ' 'To whom mrrcspondcncc should bc addressed Thrs work was initiated
at
th Ilniversitc dc I.ausanne
I"] Hctarylnicrencs. Part 7 Financial support by the Schweiunschcr Nationalfonds (1972- 1977). the Deutsche F o r r h u n b z g c m c i n W t . and thc Fonds der
Chcmischen lndustrie (1977- 1979) is gratefully acknowledged We arc indebted
10 Prof G. M u i n (Gicssen) for chc use of his matrix photolysis cqnipment. This
work is taken i n part from the Docmral lhcsis of C 7 h c l n z ( h u s a n n r . 1977)
and the Diploma Thesis of € Tughafern (Lausannc. 1976). and was presented in
pan by E. Tqlu?ferri and C Wenfrup. Autumn Meeting of the Swiss Chemical
Socnty. Bcm. O l l d v r 8. 1977 --Part 6 . [l].
566
Q V e r l q Chemrc. OmbH. 6940 Wernherm. IQRO
King contraction to (8) also occurred by thermolysis of
either (1) or (-7) in benzene solution in a sealed tube at 160180°C (59 and 88%, respectively). In addition, the solution
thermolyses of (I) and (3) in various solvents always afforded a yellow dimer in variable yield (e.g. 57% from ( I ) in
cyclohexane at 180 " C for 72 h; 25% from (3) in mesitylene at
165 "C for 240 h). The infrared, "C-NMR, and mass spectra
of the dimers obtained from ( I ) and (3) were identical, and
the structure ( I 1). possessing the novel imidazo[l,2a ] [ 1,3,5]triazino[6,5-a][1.3,5]triazepine ring system, was deThe solution thermotermined by X-ray
lyses also afforded the amines (7) and (9), respectively, which
are the products expected from hydrogen abstraction by the
triplet ground state nitrenes (4) and (6). The best yields of
amines were obtained by decomposition of (1) and 13) in a
1 : 1 mixture of octanethiol and mesitylene at 150 " C for 16 h,
giving 10% of (71, and 20% of (9), respectively. It was established that no (9) was formed from (f), and no (7) from (3).
An interconversion of the nitrenes (4) and (6) is therefore excluded.
When (1) was labeled with "N (90 atom-% i5N1'J),a subsequent flash vacuum thermolysis gave (8) labeled exclusively
in the ring, as shown by hydrolysis to l-['5N]-2-phenylbenzimidazole. A direct ring contraction (4) + (8) is therefore exclud~d~'~.
Since (I) did not give any (9) or (fO), the reaction
(4) -+(6) + (8) is also excluded. The only reasonable precursor
for (8) and (If) is therefore the cyclic carbodiimide (S).
When starting from the quinoxaline (31, a direct ring contraction (6)+ (8) cannot be excluded, but since the same dimer (11) is obtained, the nitrene (6) must isomerize at least in
part to (5). The presence of the triazepine ring in (fl) indicates that this is a rearrangement product of an initially
formed carbodiimide dimer.
Proof for the formation of the cyclic carbodiimide (S) was
obtained by photolysis of the aside (2), matrix-isolated in Ar
0570 OXJ3/80/0707 0566
S 02 50/0
An,?ew Chem Inr Ed Ens/ 19 (lY80) No 7
at 10 K [A > 375 nm]. The azide absorptions disappeared rapidly, and were replaced by intense carbodiimide absorptions
at 2010 and 1610 c m - I . The carbodiimide was stable at 10 K,
but the bands disappeared irreversibly on warming of the
matrix.
The ring expansion of other arylnitrenes and -carbenes has
been described clsewhere12.x1.
However, this is the first time
that a common intermediate--the seven-membered ring carbodiimide (5)-has been shown to be involved in the gas
phase, in solution, and in a matrix.
Rcccived. January 25. 1980:
revised Ma) 20. 19x0 [Z 508b IF.]
German version: Angcw. Chem 92. 556 (1980)
CAS Registry numbers.
/ I ) . 6199-41 -8.( 2 ) . 63399-59-7. ( 3 ) . 74144-28-X: /5). 74144-29-9: 17). 1022-44-2:
/ X t . 55x10-22-5: (Y). 33488-29-8. ( 1 0 ) . 243-59-4 / I / ) .74144-30-2
[ l ] R. Harder. C Wenrrup. J. Am Chem SN. Y8. 1259 (1976).
121 C Wenrrup in R . A . Abrumoi.irr.h. Reactive Intermediates. Vol. 1 . Chapter 4.
Plenum Piers. London 19x0. p p 263-319 (submitted in August. 1977)
[3] c'. Wenrrup. <.. ThhProz. Helv Chim. Acta 59. 256 (1976): C. Thiruz. f : W.
Wrhrli. C Wenrrup. ;bid SY. 259 (1976).
141 We have uhserved the valence tautomeric azidcs and diazo-compounds generated froni several tetra7.olo and triacolo-azinesand -diazino in a similar
manncr: fI - W Winrer. C Wwrrup. unpublished results.
IS] ! X I . m p. I10 'C. 1R (KBr): I*( 2200 c m - ' : ' H - N M R (CDCI,): 6 7 3-8 3.
maah spectrum. m / e 220 ( [ M + I ] ' , 17.7'?6). 219 ( M ' . 100). 2IX ( [ M - I ] ' .
I3 4 ) (10) was identilied hy comparison with an authentic sample. 6. M.
Badger. P J . ,%'elson. J. Chem Soc IV62. 3926.
161 / I / i crystall17.ed from CHCI, with one molecule of crystal solvent.
m.p. 257- 258'C. space group Pi. Z = 2 Crystal data
C.,H,,N,.ClKI,.
a = 1218.0(1). b=986.0(1). c.=12590(1) pm: n=100.70(5). p = 1 1 0 7 3 ( 5 ) .
y = YS.66(5)" 3039 reflections were measured with CuK.. radiation on a twocircle diffractometer 2242 \ymmetry indcpendent reflections with IF1 > 2 0 ~
were used for the determination of thc structure. which was relined to
R = 0.103. The iriacepine ring has a pronounced boat form. N( 1) being qudsipyramidal
171 When the thermolysis of '5N-ldbcled / 1 ) to (8)was carried out in so1ution.
2 7X'b of the label was found in the bcnzimidazole ring: thus 1 2 2 % o f direct
ring contraction. ( 4 ) - / / may takc place undcr these conditions. Direct ring
contraction in pyridylnitrenes has been described [ 11
1x1 0 L C'huprnun. J - P Le Roux. J Am. Chem. Soc IMJ. 282 (1978). 0. L.
Chapman. R. S. Sheridan. ibid. 101. 3690 ( 1 979).
cb-/trm-lris-[ 2.1.1]u-homobenzenes;
Synthesis and Stereochemistry of [,2 +,2
Cycloreversions'"'
+ ,2]-
By Horst Prinzbach. Hans-Peter Schul, Dieter Hunkler,
and Hans Fritzl'l
Dedicated to Professor Wolfgang Luttke on the occasion
oJ his 60th birthday
The cis-/trans-isomers of tris-[ 1. l . 1j-a-homobenzenes differ in their tendency to undergo ("2 + -2 t ,,2] cycloreversions. This-preparatively exploitable-. differentiation is determined stereoelectronically and should increasingly alter in
favor of the truns compounds in transition states with more
than nine ring members. Thus, for the tris-[2.1.1]-, trisit could be expected, with
12.2.11- and tri~-[2.2.2]-skeletons~'~
overall increasing activation barriers, that the trans-compounds also increasingly undergo [-2 + ,,2 + "21 cycloreversions12'. However, it was questionable whether "trishomoaromatic" stabilization in thc stereoisomeric ten-, clcven-, and
['I
Prof Dr f I Prinzbach. Dip1 Chcm H -P Schal. D r D Hunkler. Prof Dr
if Fritz
Lehrstuhl fur Organische Chemic der Univcratat
Albertstrasx 21 D 7800 Freiburg (Germany)
["I
This work was supported by the Deutsche Forschungsgcmeinschaft and the
Fonds der Chemischen Industrie W e thank D r H Mader. BASF. for carrying
out nurnerou? G U M S mcdsurcmentF
Angcw Chem Ins Ed 5ngI I Y (1980) No 7
twelve-membered transition states would be sufficient to favor the "internal" cycloreversion process over the "external"
competing reactions.
For our initial thermolysis studies on tris-[2.1.1] systems
we synthesized the cis-/truns-isomeric tris-[2.1. I]-ketones (5)
and (10) from the bis-[2.1]-ketones ( I ) and (6)I'l. respectively. The C O function in (1) and (6) should sterically facilitate
homologization and retard the Cope reaction typical for the
corresponding 1,4,7-cyclodecatriene in the expected thermolysis products (12) and (14). The ketone (5) is also o f interest
as potential precursor for the still unknown cis-tris-(1.1.1]
skeletal unit.
The cyclopropanation of / I ) and (6) meets with the usual
diffi~ulties~~l.
Satisfactory-though not always completely reproducible-results could only be achieved after reduction to
the respective endo-alcohols (2) and (7). Reaction of (1) with
NaBH, or diisobutylaluminum hydride (DIBAH) afforded
(2) and (3) in the ratio 6: 1 and 10: 1, respectively (total yield
(1)
12). x = OH, Y = H
f3), X = H, Y = O H
(4)
'71, X = OH, Y = 11
( 8 j . X = H, Y = OH
(9)
of 94% in each case). Almost pure (7) [ < 5% (8). total cu.
90%] was obtained on reaction of (6) with NaBH,. On subjecting (2) to a modified Conia procedure['], a mixture of alcohols and their methyl ethers is obtained in ca. 50-60%
yield which have to be separated by preparative layer chromatography (CH,Cl7/SiO2). The main product (40%) is the
endo-[2.1.1]-alcohol (4); the methyl ethers (4a) and (46)
could also be identified. (7) is cyclopropanated in comparable yield (50-60%) on the side of the OH-group to give (9)
and the side product ( 4 4 . After oxidation with pyridinium
chlorochromate (CII2CI2, 20 "C), the colorless oily ketones
(5) and (10) ('H-NMR data, see Table 1) are each obtained
in ca. 60% yield.
The cis-ketone (5) is stable in CCl, solution up to cu.
120°C; at higher temperatures (ri,2(1500C)=40 min) it is
converted quantitatively (TLC, GC, 'H-NMR) into the conformationally flexible Z,Z,Z-2,5,8-cyclodecatrien-l
-one ( I 2).
This uniform behavior is also observed on gas phase pyroly(no products such as ketenes or
sis (350°C; quartz
cyclooctatriene''1 resulting from the cleavage of "external"
bonds) Calculations based on kinetic data measured ('€1NMR) between 135 and 160°C in degassed samples and
evaluated according 'to the first order rate law gave the parameters E , = 1 4 0 ~ 2 kJ mol-'
(logA = 13.8) and
A H * = 1 3 7 + 2 ' k J mol-' ,(AS*= 8 + 3 JK-")['I The unifor-
0 Verlag Chemre. GmbH, 6440 Wetnheim, 1480
0570-0833/80/07070567
S 02 5010
567
Документ
Категория
Без категории
Просмотров
1
Размер файла
233 Кб
Теги
cyclic, rearrangements, nitrene, carbodiimides
1/--страниц
Пожаловаться на содержимое документа