close

Вход

Забыли?

вход по аккаунту

?

Doubly Metalated 2-Propene-1-thiol Thioacrolein Dianion.

код для вставкиСкачать
4) Thermochemical increment calculations d o not reveal any
diffcrenccs in the molar heats of formation AH:' of ( 1 ) and
(-7) even aftel- taking special account of the H/H interactions
(staggered or eclipsed).
Since the adducts ( I ) and ( 2 ) have (almost) equal energy
contents it does not appear surprising that the same activation
energies are found for the 1.3 shift and cycloreversions (within
the limits of error) if the (possibly polar) diradical (3) is
formed initially without any change in multiplicity. The
"allowed" reaction (2) +( ( 4 ) + ( 5 ) ) is not energetically
favored. and the differences in the reaction rates are due
almost exclusively to thedifferent frequency factors (cf. formula
scheme). The symmetry-corrected rate constant ( k l + k11)/2 is
5.6 times greater than kttl (see above). This kinetic disadvantage
of the retro-Diels-Alder reaction suggests that the eclipsed
arrangement of benzhydrylic and allylic hydrogen atoms in
( I ) (dihedral angle cu. 12""0'; 'H-NMR coupling constant
J = 9.0 Hz"') enhanccs the probability of cleavage of thc C--C
bond compared to the staggered arrangement in ( 2 ) (60 r t O i :
3.0 Hzl").
In both cases the intermediate (3) is formed which has the
possibility of rotation about the exocyclic C--C bond. and
finally the products ( ( 4 ) + ( 5 ) ) and (2) are obtained in
the ratio Xl~/kl=80.5/19.5. In addition, molecular models prcdict that the stabilization route ( 3 ) + ( I ) must also be operative. This reaction, which cannot be detected by UV spectroscopy mainly because the primary reaction of (I) on pyrolysis
is ca. 11 times faster, would become of preparative significance
ifthedecomposition ofthe [4+4] adduct ( I ) could beprevented : selective irradiation of anthracene ( 4 ) in cyclopentadiene
( 5 ) (0 C) affords a photointermediatel'l which is likewise
assumed to have formula ( 3 ) (presumably in similar rotational
and vibrational states). Kinetically controlled reaction then
yields ( I ) and ( 2 ) in the ratio 58/42'"'.
The utility o f direct comparison of thermal and photochemical
two-step reactions is apparent from the results obtained on
irradiation of adduct ( 1 )I1'I. The "allowed" reactions afford
80 %
' I of ( 4 ) and I8 YOof ( 2 )( 4 = 0.26 +0.06: CH,CN; 20 C)[sll.
The measurable deactivation ratio of thermally and photochemically generated ( 3 ) is thus, as expected, equal (within the
limits of error). Hence the conclusion is justified that intermediate ( 3 ) generated from ( I ) underpoes stabilization to
( ( 4 ) + ( 5 ) ) , ( / ) , a n d (2) in theratios4.1:1.4:1.0.
Received. December I I . 1973:
revised: January 2, I974 [ Z 10 IE]
German version: Angew. Cheni. 86. 523 11974)
Doubly Metalated 2-Propene-1-thiol
Thioacrolein Dianion['I [**I
By Ktrdlirin: Gciss. B~w7iirrrtlSmr-;t7y, Rciriimd P i e r ~ r .and
Dieter Seebach"]
As exemplified by eq. (1) and (2), carbonyl compounds add
electrophiles (E) at the (Y position (EZreaction[") and nucleophiles (Nu) at the B position (N3 reactiont2]).Unipoiung at C"
is, in principle, possible with heterosubstituted allylic anions
provided that they are susceptible to attack by electrophiles at
the y position to the hetero atom; with X = S R the 2 position
is preferentially attacked [eq. (3)]". 3 1
In this communication we report a novel allylic anion. the
doubly metalated 2-propenethiol (/)I4, 5 1 , which reacts preferentially in the >( position with a variety ofelectrophiles. including alkyl and benzyl chlorides and bromides, epoxides, aliphatic. cycloaliphatic. aromatic aldehydes and ketones, and
dimethyl disulfide. The dilithio derivative is formed quantitatively by treating a 0.3-0.9~ solution of the thiol in T H F
with 2.1 equivalents of n-butyllithium ( 1 . 6 ~in n-hexane) in
the presence of 1-2 equivalents of tetramethylethylenediamine (TMEDA) for four hours at 0°C. As shown in Table
1, the y/r* ratios["' in which products ( 2 ) and (3) are formed
range from 67: 33 to 80:20 (NMR spectrum). The y adducts
[ I ] R. B Wiiidiim/;ind R. H o f / i n o i i i t TheConservation of Orbital Symmetry.
2nd t d i t . Verlag Chemtc. Weiiihetm 1972.
[ 2 ] J 4. Brr.\oii atid R. IW /folder. J. Amcr. C'hem Soc. Y.5. 2037 (1973):
and l i t e r a t u r e cited therein.
[3] S . W' Bcvisoii Thermochcmical Kinetics. Wiley. New York 196X: R.
K . L i o i i , J. Org. Chcm. 34. 3202 ( IY69).
r41 App;irentfq o u i n g to difficulties o f mensurcment ii dcc~sronof this kind
has not yet been reached for thermolyses of 1.5-cyclooctadiene a n d 4-vinylcyclohexene lo butadiene. cf. W c. E. Doering. M. Franck-Neumanii. D. Hossrliii(iiiii. m d R. 1. K < I ) ( , J.
. Amer. Chcm Soc. Y4. 3x33 (19721.
[ 5 ] G K(ri,pp. Angew. Chcm. 84. 71X (1972): Angew. Chem. internxt. Edit
/ I . 718 (1972): Lichtgs Ann. Cheni. IY73. 844.
[6] Temperature constancy +0.1 "C; measurements conducted in a n ultrathermostat (Lauda. type R10/2) with calibrated fine thermometers.
[7] A d j u s t m e n t of/,,, (fi-um less precisely determinable initial rates: vartiitton
in bteps of 0.3 'A,) by using the more accuratcly determinable quantities
are formed almost exclusively ( >95 YO)in the cis-configurationl'l. The isomers ( 2 ) and (3) may be separated by preparative thin-layer, column, or gas chromatography.
The use of ( 1 ) as synthon in analogy to eq. (3)is demonstrated
by the reaction of the products ( 4 ) and ( 8 ) of type (-7)
in Scheme 1. We have developed a new procedure for the
.~ .
[*] Dipl.-C'heni K.-H. Gciss. B Seuring. K. f'trtcr. :ind Prof Dt. D. Secb,icli
I n s t i t i i t fiir Or_rantschc ('hemie des Fachbcreichs 14 ('hcmic dcr C l i i i vet-sitiit
63 Gicsscn. Ludwtgstrassc 2 I IGerm:itiy)
['*] This uork w i i s supported hy the Deutschc Forscliungsgciiietiiscliaf~
and the Fonds der C'hemischen Indiisti-ic
Angrw. Chrm. infr.mur. Edit. / Vr,/ I3 ( 1 9 7 4 ) / No. 7
479
Yield. reaction conditions. iind -/ Y ratios in the reactions of ( I ) with electrophiles to give ( 2 ) + ( 3 ) .
Table I
__
.
~
I:'
.~
... ..
.. -. .
~
~
EL
. _. .
.~
C ' l i Br
~-
~ .
C~HIBI
Ii-CioH 2 1 Br
C,)HiCH2Br
i i - C I , I H 2Br
1
C,,H ,CH?Br
ll-C7H,,('1
ii-C<,Ht.I Br
ii-CKHl-Cl
i-CrH-CI
(CH > \ 6 i C \
2,Z-Dimethyloxirane
<''Hic'HO
(iI1.C.f 1 0
Cyclopentanone
(.c,H <COCHI
(CoH<)'CO
CH ISSCH j
~~
. ~ .
Yields
[ '7.3
Ial
of(zi+(3J[b]
A
A
A
65
90
67
75
90
87
80
76
86
69
89
70
95
88
70
-!1
Ratio
..
(')I ? I
c
CH $ 1
CI1,I
CI,HICH'Br
C,,H ;CH ZBr
2,2-Dimethyloxirane
CH.tI
CHII
CHAI
CHzl
CHJI
CHII
C
c'
I= f
3 i]
~
c
B
A
B
C
C
c
c
B
..-~
_
77 23
77.23
73/17
76 24
78,'22 [c]
74 26
6X. 32
76/24
78/22
74.26
80,120
__..
~- .[a] A : 2.1 equivalents of E ' are added at - X O C by syringe. then the mixture is allowed to warm to 20 C overnight.
B: ( 1 ) 1s reacted uith 1.03 I I equivalents of t' for I 11 at -80 C. 1.1 equivalent of E' is added. and the mixture
jbarmed to rooin temperature.C: as B. but E' is added u / ! w slowly warming to room temperature. Workup see
ref [4].
[h] The yields (not optimized) were determined by NMR spectroscopy of the crude products of 2.- IOmrnol runs
[c] See Scheme I , compound ( 4 ) .
.
. .
~ . . -~
~-
-~
.
Reaction
conditions
~
.
~
.
~
.
~
.
~
-
~
.....
-1
(u). X = 0; ( b ) , X = (OCH,),
[3] E . J. C m q and B. W E t . i i . k . ~ ~unpiibiished
i.
results 1966.!67; B. W
Ericisoii, PltD thesis, Harvard University 1970: J . F . Bic//nicrnn and J . B.
Duceh, Tetrahedron Letters IY6K, 5629: IY6Y. 3707: K . Kolido rr ul.. Chem.
Commun. 1972. 131 I : D. Srrbodi. M. Koib. and B.-Th. G r i h i . Angew.
Chem. 8s. 42 (1973): Angew. Chem. internat. Edit. I?. 69 (1973). P L,.
Srotiri. and R. E Hortiish, J. Amer. Chem Soc. Y.5. 4444 (1973): K . Oshiniu
cr u . . ihid. 95. 2693. 4446. 5803. 7926 (1973): D. 4. Errins and G . C. Aiiclrrn.s,
Accounts C h e m Res 7. 1974. i n press. and literature cited therein.
[4] Doubly metalated thiohenzyl alcohol: D.Seebach and K.-H. Geiss. Angew.
Chem 86, 202 (1974): Angew. Chem. internat. Edit. 13, 202 (1974).
[5] Prof. M. Sr/ifo.ssrr.Lausanne. kindly informed us that 2-propcne-1-thiol
and 3-methyl-2-butene-I-thiol have been doubly metalated independently
in his laboratories
161 Determined from the NMR integration ratios of the following signals:
?-sulfur hydrogens of the group E'. the vinylic I"wits all other hydrogens.
and the terminal vinylic hydrogens I crsiis all vinylic hydrogens. The NMR
spectra of some of our products aie identical with those described by B.
W. Eiicirron (Thesis, H a n a r d University 1970) who obtained compounds
( 2 ) and (3) from metalated thioallyl ethers. All new products show spectra
in accordance with the structures given here.
[7] E . J . Corer. and B. W
Scheme I . Sulfur-free products from adducts ( 4 ) and (8) of the dianion
(;ill reactions Mere carried out at 20 C). 141-+151: CH.$SH!HCI &%is
in benzene, 3min, 1007;;
/ 4 ) - ( 6 a j : 4,5 equiv. NBS in acetonitrile/H,O.
2min. 73%; (41-(6b):
as above but in anhydrous CH,OH, 85",,:
( 5 ) - ( 7 u ) : 4.5 equiv. NBS, 5 equiv AgNO, in acetonitrile/H,O. 3min.
6 0 % : ( 5 ) - ( 7 h ) : as above but i n anhydrous C H 3 0 H . 7 0 % : / 8 ) + ( 9 ) :
4.3 equiv. NBS in CH,OH. 2min. 7 4 %
(1)
conversion of methyl vinyl thioethers such as (4) into aldehydes ( 7 u ) which involvesaddition ofthiol to forma thioacetal
( 5 ) that is subsequently hydrolyzed by known methodsE2'.
N-Bromo~uccinimide~~'
converts ( 4 ) into the rx-bromo aldehyde ( 6 u ) in aqueous acetonitrile, while the bromo acetal
( 6 h ) is produced in methanol; similarly, the cyclic brorno
acetal ( 9 ) is formed from the benzaldehyde adduct (8).
Received: May 15. 1974 [ Z 30 IE]
German version. Angew Chem. K6. 484(1974)
[ I ] From the PhD thesis of K.-H. Griss and the Diplomarbeit of B. Swi'iny,
Universitiit Giessen 1974.
[2] Reviews on Umpolung of carbonyl reactivity: D. Seebach and M . K o f h ,
Chem. Ind. (London), IY74, in press; D. Seebach,Angew. Chem. 81,690(1969);
Angew. Chem. internat. Edit. 8, 639 (1969); D. Seebach, Synthesis 1969. 17.
and literature cited therein.
480
Ei.ic/,.\oii,
J. Org. Chem. 36. 3553 (1971).
Dynamic Stereochemistry of the Degenerate DiazaCope Rearrangement[**]
By Fritz Viiqtle and Ernst Goldschmitt[*]
A further milestone was passed in the theory ofvalence isomeri-
zation when, in 1971, Dewar"] postulated that 3,7-diazasemibullvalene has to be formulated as a nonclassical molecule
[bishornopyrazine (1 )] in the ground state.
While experimental proof of this prediction is still forthcoming,
the recently described thermal valence isomerization of 1,3,4,6[*] Prof Dr. F. Vogtle and Dlpl.-Chem. E. Goldschmitt
lnstitut fur Organische Chemie der UniversitPt
87 Wurzburg, Am Hubland (Germany)
[**I
This work was supported by the Deutsche Forschungsgemeinschaft
and the Fonds der Chemischen Industrie.
A n g m . Chrm. internat. Edit. Vol. 13 ( 1 9 7 4 ) 1 No. 7
Документ
Категория
Без категории
Просмотров
1
Размер файла
219 Кб
Теги
propene, thiol, double, dianion, thioacrolein, metalated
1/--страниц
Пожаловаться на содержимое документа