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Thiocarbonyl ylides. An approach to “tetravalent sulfur” compounds.
Tetrahwzlron Lrtters No. 13, pp. 1987-l')YO, 1970.
THIOCARBONYL YLIDES.
Printed in Great Britain.
Pergamon Press.
AN APPROACH TO "TETRAVALEN?? SULF'UR" COMPOUNDS.
Richard M. Kellogg and Siek Wassenaar' Department of Organic Chemistry, The University, Bloemsingel
10, Groningen, The Netherlands
(Received in UK 23 March 1970; accepted for publication 16 April 1970)
We wish to describe a rational approach to the generation of thiocarbonyl ylides, CL), a new class of reactive intermediates. Thiccarbonyi ylides, as depicted in eq. 1, may be described in terms of l,j-dipolaF*, biradical, or "tetravalent sulfur"3-5 resonance structures.
6
The previously described azomethine7 and carbonyl ylides
a
are related formally to
1 by replacement of sulfur by nitrogen and oxygen, respectively.
(1)
Two orbital symmetry allowed9 paths for the generation of 1, viewi-ng it as rn isoelectronic with the ally1 anion'", were considered. Most obvious was the conrotary electrocyclic ring-opening of an episulfide, a type of reaction which ha s been effected with appropriately substituted azirines 7 and epoxides.
8
An alternative and, for us, more successful attack
on the problem makes use of the thermaliy induced loss of nitrogen from l,S,b-thiadiazolines which are, of course, the expected 4s i 2
(2)
cycloadducts of _l_with nitrogen (eq. ;!,.9
The pivotal compoundss2_, cardinal to the iatter approach, were obtained from the previous-y reported 1,3,4-thiadiazolidines " diethylazodicarboxylate.
12
This dehydrogenation
in ether solution to give stable &, 1579 cm-'
( N-N
2 :vhich were dehydrogenated using
proceeds smoothly with 2
at room temperature
in 54% yield, mp al-82 " (without decomposition);
j; uv max (96% EtOH) 2890 b! (a 342) and 3220 a (F:2~8).""~ 1w7
ir (KBr)
kJ.33
R4\ /R3 c.\ ;s
(21
C/f R/ 2
'R
1
a) R,,R2 = R3,R4 = (CH215 b) R, = R3(R4) = Et R2
= Fi4(R3) = H
Either in the meit at 100' or in hydrocarbon nitrogen smoothly (eq. 3) to give in
99% yield th& thiirane &,
C6H6) 198.2; uv max (96% EtOH) 2590 a ( F= 50).15 converted &
loses
mp 75-77o; moi. wt. (osmet. in
Reaction with G-butyllithium'6
in ether
in 77% yield. Attempts to intercept the suspected
to cyclohexylidenecyclohexane
intermediate k
solution at go', &
with either trans-stilbene
or dimethyl acetylenedicarboxyiate
met with failure.
However, when &
was allowed to decompose in the presence of an equimolar quantity of diethyl-
azodicarboxylate
a mixture was isolated consisting of 5
ir (KE?) 1710 cm-' ( NC=0 ); nmr (X14)
mp G-67.5',
(33% isolated) and 2
6 4.10 (q, 4, ,J = 7.0 Hz, CCgI&,, 8 1.25
(t, 6, J = 7.0 Hz, C% ), and 6 1.36-2.11 (broad muitiplet, 20, (C&),. LJ react with diethylazodicarboxylate
(42% isolated),
14
Thiirane -4a fail<- to
under similar conditions.
Et02C\ ia
+
@Tg
2%
‘Et02CN=NC02Et
a
a
5a Et02C,-N,C02Et a H*, Xk Et
H
H
/<
+
b-_+ Et02CN=NC02Et
S
Et
Et (unstable)
sb
4b Me02CCSC02Me I MeC2C,C_C,C02Me H.
-
EtLx: S
Et
3-hexene
(4)
No.23
1989
Analogous reactions were carried out with the known cis and trans-2. 17 Here, however, an enormous difference was found in the thermal stability of -2b as compared to a.
When equimolar amounts of 2
and diethylazodicarboxylate
for 5 hr, diethylhydrazinodicarboxylate
in ether solution are held at -10'
is formed in 73% yield along with an unstable compound
18 uv max (C5H,2) 3180 w and 2820 8 which is most likely j2&. Above 10' this unstable compound 3 c loses nitrogen and yields -cis and trans-2,j-diethylthiirane
(2)
and some -cis and trans-j-hexene
(36% combined yield after distillation) as well as some cycloaddition product 2 latter compound, ir (neat) 1710 cm-', nmr (CCl4) F 5.48 (overlapping
(eq. 4)."
The
triplets, 2, J = 7.2 Hz,
L-C-H), 6 4.23 (overlapping quartets, 4, J = 7.5 Hz, (3X2), 6 1.40-2.00 (complex multiplet, 4, Cg2CH), 6 1.28 (t, 6, J = 7.5 Hz, Cg3), and 6 0.97 (overlapping triplets, 6, J = 7.2 Hz, 'X3) is obtained in 67% yield if an extra equivalent of diethylazodicarboxylate
is added to the
reaction mixture prior to warming to room temperature. If the unstable -2b is warmed to room temperature in the presence of one equivalent of dimethylacetylene of 2,5_dihydrothiophene
&
dicarboxylate,
a 20s yield
(with expected spectra) is obtained.
These observations are congruous with our supposition that thiocarbonyl ylides should be generated during thermal decomposition of thiadiazolines 2. As expected, these intermediates cyclize readily to the thiiranes but also add to appropriately
substituted 2rr
systems at a competitive rate. In this respect, their behavior agrees fully with that of azomethine and carbonyl ylides. We are now investigating the stereochemistry
of the ringiclosure
and cycloaddition reactions of 2. Rather to our surprise, 2, cyclohexanone azine as the only demonstrable
upon irradiation, lost sulfur cleanly to give
organic product (eq. 5).
(5) a This reaction pertains even at -170' in a methylcyclohexane
matrix. This dichotomy of thermal
and photochemical behavior may arise from the absence of an orbital symmetry allowed path for the loss of nitrogen from 2
(assuming excitation to be centered in the azo chromophore) whereas
a cheletropic 9 elimination of sulfur is an allowed process. This reaction finds some precedent in the photochemically
induced elimination of sulfur dioxide from butadiene sulfones.
20
::o. 5
1990
Weare indebted tc Professors J. Stratrng and Hans Wyn'c?rr;for their interest
Acknowledgement.
Dr. J.B.F.N. Engberts suggested diethylazodicarboxylate
in this work.
as a dehydrogenating agent.
REFERENCES
1. NATO Posfdoctoral Fellow, 2.
R.
Huise;en,
An~ew.
lgbg-1973.
Chem., 2,
i-04 (196:) reviews 1,3-dipolar additions.
orbital symmetry considerations
of
see A. Eckell, R. Huisgen, R. Sustmann, G. lu'allbillich,
D. Grashey, and E. Spindler, Chem. Be?., s, Chemistry”,
?or applications
;ohn
2192 (19671;
aiS0
E.b!.
Kosower, "An Intl,oduction
‘Wiley
and Sons, Inc., New York, 1J.I'.1968, :'I_‘ 2O?-;?i&. :. ?i L ifur" isomers of t‘fliophenehave been synthesized Ly Cava axd Scnlessicger. 3. "Tetravalent cu' to Physical Organic
4. M.P. Cava and ;.E.p<. Husband.~, v. ~mer. Chem. SOC., 5. J.I). 3ower and R.H. Schles;inger, w.,
y,
6. Other resonance titructures can be drawn, of course. sLtbsti:uents are ccp&egar. ssabilization
3952 (1969).
9,
6891 (1969). We assume here that t!le earbor?
Should significant d orbital paxicipation
be involved in the
of 1, C-z=C, then the cyiindricai symmetry of t:hese orbita:s might passiuly
lead to an es:enLially or;liogona~ arrangement of substituents. 7. See, for examp-e: R. Euisgerl, 3::.Scheer, and H. Yuber, J. Amer. Chem. SW.,
82, 1745 i196,“
and references contained Ll;e-ein. Also R. Huisgen and H. Wader, Angew. C&m.,
3 . W.2. Linn and R.E. 3enson, J. Amer. Chen. SW.,
82, $5’7
$2, 621 (lg@'j.
!lg65).
':isodxardand 9. Hoffmann, Angew. :hem., 81, g. R.O. EzE [9[ (1965). iO. R. Hoffmann, J. Amer. "hem. Soz., 92, 1475, (1968) for discussion of carnony. ylides. 11.
I(. J?tih:maiul, ;. Prakt. Chem., 5, 785
1%.
F.
(1359).
Ycneda, K. S~xjki, and ‘J. Xitta, J. Amer. Chem. Sot., 88, 2328 (1$6!.
ij. Csmpare ywith data of C.G. Overoerger, N. Weinshenker, and ,.-F. Anselme, a., 82, 5564 1 -. (;$lh:a; for> a A -pyrazollne; also PI. Rieber, J. Alberts, 5.13. Lij-&y, and I:.I*I. I,emal, w., 9,
$68
:1969).
14. Correct elemental analyses 'were obtained for all new compounds; mass spectra wcortied 1‘;.111y with assigned structures. 15. Absorption at -~a 2600 3 216 (195&J.
1s characteristic of eFis.x'fides: R.E. Davis, ,J. Org. C&m.,
16. F.G. 3ordiuell, !i.!+?. Anderser;, and 3.M. Pitt, J. Amer. Chem. SW., 17.
A
cis, ;rar,s mix:ure of 2,
recrg;taLiization
mp d-75'
(lit."
and .s:lb_i:Tbxion.A wrtion
5, -
l&2
25,
(1954).
o\ was cctained after cainsrakirlg
mp ‘72 j
of ;ilis !vzl,krazz rnoht capa'_:> 3o;x :‘yMiss
Mieke l:oteboom. 18. The cause of tie enormous dif_'erence in stabiiity of & and C-5 (ring flip with &) Chem. Sot.,
z, ‘
ard 21; migh: lie ir inverziori at Z-3
during loss of nitrogen; cf. E.;. Allred and R.L. Smith, J. Amer .
07bi (1969;; H. Tznida, S. Teratake, ii. Hate, a!id 1\"1. :iatanabe, Tetrahedron
Letters, a, 531, 5,345. Sut see A. Oberlimmer and Z. Riicl~ar~di, ijid., m, p_ 19. The j-hexenes appare:1:!::arise direct-y diring tl:e decomposit'on of -2b. 20. J. Sailie. and I.
i?:c;t,s, .I. Amer. ThepI. .:oc., $2, 252 ‘
:::j&, .‘
4635.
THIOCARBONYL YLIDES.
Printed in Great Britain.
Pergamon Press.
AN APPROACH TO "TETRAVALEN?? SULF'UR" COMPOUNDS.
Richard M. Kellogg and Siek Wassenaar' Department of Organic Chemistry, The University, Bloemsingel
10, Groningen, The Netherlands
(Received in UK 23 March 1970; accepted for publication 16 April 1970)
We wish to describe a rational approach to the generation of thiocarbonyl ylides, CL), a new class of reactive intermediates. Thiccarbonyi ylides, as depicted in eq. 1, may be described in terms of l,j-dipolaF*, biradical, or "tetravalent sulfur"3-5 resonance structures.
6
The previously described azomethine7 and carbonyl ylides
a
are related formally to
1 by replacement of sulfur by nitrogen and oxygen, respectively.
(1)
Two orbital symmetry allowed9 paths for the generation of 1, viewi-ng it as rn isoelectronic with the ally1 anion'", were considered. Most obvious was the conrotary electrocyclic ring-opening of an episulfide, a type of reaction which ha s been effected with appropriately substituted azirines 7 and epoxides.
8
An alternative and, for us, more successful attack
on the problem makes use of the thermaliy induced loss of nitrogen from l,S,b-thiadiazolines which are, of course, the expected 4s i 2
(2)
cycloadducts of _l_with nitrogen (eq. ;!,.9
The pivotal compoundss2_, cardinal to the iatter approach, were obtained from the previous-y reported 1,3,4-thiadiazolidines " diethylazodicarboxylate.
12
This dehydrogenation
in ether solution to give stable &, 1579 cm-'
( N-N
2 :vhich were dehydrogenated using
proceeds smoothly with 2
at room temperature
in 54% yield, mp al-82 " (without decomposition);
j; uv max (96% EtOH) 2890 b! (a 342) and 3220 a (F:2~8).""~ 1w7
ir (KBr)
kJ.33
R4\ /R3 c.\ ;s
(21
C/f R/ 2
'R
1
a) R,,R2 = R3,R4 = (CH215 b) R, = R3(R4) = Et R2
= Fi4(R3) = H
Either in the meit at 100' or in hydrocarbon nitrogen smoothly (eq. 3) to give in
99% yield th& thiirane &,
C6H6) 198.2; uv max (96% EtOH) 2590 a ( F= 50).15 converted &
loses
mp 75-77o; moi. wt. (osmet. in
Reaction with G-butyllithium'6
in ether
in 77% yield. Attempts to intercept the suspected
to cyclohexylidenecyclohexane
intermediate k
solution at go', &
with either trans-stilbene
or dimethyl acetylenedicarboxyiate
met with failure.
However, when &
was allowed to decompose in the presence of an equimolar quantity of diethyl-
azodicarboxylate
a mixture was isolated consisting of 5
ir (KE?) 1710 cm-' ( NC=0 ); nmr (X14)
mp G-67.5',
(33% isolated) and 2
6 4.10 (q, 4, ,J = 7.0 Hz, CCgI&,, 8 1.25
(t, 6, J = 7.0 Hz, C% ), and 6 1.36-2.11 (broad muitiplet, 20, (C&),. LJ react with diethylazodicarboxylate
(42% isolated),
14
Thiirane -4a fail<- to
under similar conditions.
Et02C\ ia
+
@Tg
2%
‘Et02CN=NC02Et
a
a
5a Et02C,-N,C02Et a H*, Xk Et
H
H
/<
+
b-_+ Et02CN=NC02Et
S
Et
Et (unstable)
sb
4b Me02CCSC02Me I MeC2C,C_C,C02Me H.
-
EtLx: S
Et
3-hexene
(4)
No.23
1989
Analogous reactions were carried out with the known cis and trans-2. 17 Here, however, an enormous difference was found in the thermal stability of -2b as compared to a.
When equimolar amounts of 2
and diethylazodicarboxylate
for 5 hr, diethylhydrazinodicarboxylate
in ether solution are held at -10'
is formed in 73% yield along with an unstable compound
18 uv max (C5H,2) 3180 w and 2820 8 which is most likely j2&. Above 10' this unstable compound 3 c loses nitrogen and yields -cis and trans-2,j-diethylthiirane
(2)
and some -cis and trans-j-hexene
(36% combined yield after distillation) as well as some cycloaddition product 2 latter compound, ir (neat) 1710 cm-', nmr (CCl4) F 5.48 (overlapping
(eq. 4)."
The
triplets, 2, J = 7.2 Hz,
L-C-H), 6 4.23 (overlapping quartets, 4, J = 7.5 Hz, (3X2), 6 1.40-2.00 (complex multiplet, 4, Cg2CH), 6 1.28 (t, 6, J = 7.5 Hz, Cg3), and 6 0.97 (overlapping triplets, 6, J = 7.2 Hz, 'X3) is obtained in 67% yield if an extra equivalent of diethylazodicarboxylate
is added to the
reaction mixture prior to warming to room temperature. If the unstable -2b is warmed to room temperature in the presence of one equivalent of dimethylacetylene of 2,5_dihydrothiophene
&
dicarboxylate,
a 20s yield
(with expected spectra) is obtained.
These observations are congruous with our supposition that thiocarbonyl ylides should be generated during thermal decomposition of thiadiazolines 2. As expected, these intermediates cyclize readily to the thiiranes but also add to appropriately
substituted 2rr
systems at a competitive rate. In this respect, their behavior agrees fully with that of azomethine and carbonyl ylides. We are now investigating the stereochemistry
of the ringiclosure
and cycloaddition reactions of 2. Rather to our surprise, 2, cyclohexanone azine as the only demonstrable
upon irradiation, lost sulfur cleanly to give
organic product (eq. 5).
(5) a This reaction pertains even at -170' in a methylcyclohexane
matrix. This dichotomy of thermal
and photochemical behavior may arise from the absence of an orbital symmetry allowed path for the loss of nitrogen from 2
(assuming excitation to be centered in the azo chromophore) whereas
a cheletropic 9 elimination of sulfur is an allowed process. This reaction finds some precedent in the photochemically
induced elimination of sulfur dioxide from butadiene sulfones.
20
::o. 5
1990
Weare indebted tc Professors J. Stratrng and Hans Wyn'c?rr;for their interest
Acknowledgement.
Dr. J.B.F.N. Engberts suggested diethylazodicarboxylate
in this work.
as a dehydrogenating agent.
REFERENCES
1. NATO Posfdoctoral Fellow, 2.
R.
Huise;en,
An~ew.
lgbg-1973.
Chem., 2,
i-04 (196:) reviews 1,3-dipolar additions.
orbital symmetry considerations
of
see A. Eckell, R. Huisgen, R. Sustmann, G. lu'allbillich,
D. Grashey, and E. Spindler, Chem. Be?., s, Chemistry”,
?or applications
;ohn
2192 (19671;
aiS0
E.b!.
Kosower, "An Intl,oduction
‘Wiley
and Sons, Inc., New York, 1J.I'.1968, :'I_‘ 2O?-;?i&. :. ?i L ifur" isomers of t‘fliophenehave been synthesized Ly Cava axd Scnlessicger. 3. "Tetravalent cu' to Physical Organic
4. M.P. Cava and ;.E.p<. Husband.~, v. ~mer. Chem. SOC., 5. J.I). 3ower and R.H. Schles;inger, w.,
y,
6. Other resonance titructures can be drawn, of course. sLtbsti:uents are ccp&egar. ssabilization
3952 (1969).
9,
6891 (1969). We assume here that t!le earbor?
Should significant d orbital paxicipation
be involved in the
of 1, C-z=C, then the cyiindricai symmetry of t:hese orbita:s might passiuly
lead to an es:enLially or;liogona~ arrangement of substituents. 7. See, for examp-e: R. Euisgerl, 3::.Scheer, and H. Yuber, J. Amer. Chem. SW.,
82, 1745 i196,“
and references contained Ll;e-ein. Also R. Huisgen and H. Wader, Angew. C&m.,
3 . W.2. Linn and R.E. 3enson, J. Amer. Chen. SW.,
82, $5’7
$2, 621 (lg@'j.
!lg65).
':isodxardand 9. Hoffmann, Angew. :hem., 81, g. R.O. EzE [9[ (1965). iO. R. Hoffmann, J. Amer. "hem. Soz., 92, 1475, (1968) for discussion of carnony. ylides. 11.
I(. J?tih:maiul, ;. Prakt. Chem., 5, 785
1%.
F.
(1359).
Ycneda, K. S~xjki, and ‘J. Xitta, J. Amer. Chem. Sot., 88, 2328 (1$6!.
ij. Csmpare ywith data of C.G. Overoerger, N. Weinshenker, and ,.-F. Anselme, a., 82, 5564 1 -. (;$lh:a; for> a A -pyrazollne; also PI. Rieber, J. Alberts, 5.13. Lij-&y, and I:.I*I. I,emal, w., 9,
$68
:1969).
14. Correct elemental analyses 'were obtained for all new compounds; mass spectra wcortied 1‘;.111y with assigned structures. 15. Absorption at -~a 2600 3 216 (195&J.
1s characteristic of eFis.x'fides: R.E. Davis, ,J. Org. C&m.,
16. F.G. 3ordiuell, !i.!+?. Anderser;, and 3.M. Pitt, J. Amer. Chem. SW., 17.
A
cis, ;rar,s mix:ure of 2,
recrg;taLiization
mp d-75'
(lit."
and .s:lb_i:Tbxion.A wrtion
5, -
l&2
25,
(1954).
o\ was cctained after cainsrakirlg
mp ‘72 j
of ;ilis !vzl,krazz rnoht capa'_:> 3o;x :‘yMiss
Mieke l:oteboom. 18. The cause of tie enormous dif_'erence in stabiiity of & and C-5 (ring flip with &) Chem. Sot.,
z, ‘
ard 21; migh: lie ir inverziori at Z-3
during loss of nitrogen; cf. E.;. Allred and R.L. Smith, J. Amer .
07bi (1969;; H. Tznida, S. Teratake, ii. Hate, a!id 1\"1. :iatanabe, Tetrahedron
Letters, a, 531, 5,345. Sut see A. Oberlimmer and Z. Riicl~ar~di, ijid., m, p_ 19. The j-hexenes appare:1:!::arise direct-y diring tl:e decomposit'on of -2b. 20. J. Sailie. and I.
i?:c;t,s, .I. Amer. ThepI. .:oc., $2, 252 ‘
:::j&, .‘
4635.