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Synthesis of α-alkylidene-γ-lactones by intramolecular addition of alkoxycarbonyl free-radicals to acetylenes
Tetrahedron Letters, Vo1.21, No.5, pp 641-644, 1986 Printed in Great Britain
SYNTHESIS OF a-ALKYLIDENE-y-LACTONES ADDITION OF ALKOXYCARBONYL
BY INTRAMOLECULAR
FREE-RADICALS
Mario D. Bachi’
0040-4039/86 $3.00 + .OO 01986 Pergamon Press Ltd.
TO ACETYLENES
and Eric Bosch
Department of Organic Chemistry, The Weizmann lnstitote of Science, Rehovot, Israel
Abstract:a-Alkylidene-y-lactones rivatives of homopropargylic The free-radical deoxygenation dithiocarbonates2 desoxy formyl
products
of
reductive
most
of various useful,
thiocarbonylimidazolides,* (5).
Similar
ester (4) and/or
seems to follow
degradation The
alcohols.’
are obtained by treatment of chloroformate alcohols with tri-n-butylstannane.
reductions
alkanes
carbonic the
of chloroformates
acid
preparative
thionocarbonates,3,4
(5) depending
one of the mechanisms
on
scale,
extensively
and selenocarbonates.’
which
lead to the corresponding
or trialkylsilanes’
afford the corresponding
and the reaction
of
used for the
reaction
with trialkylstannane6,7
in Scheme
(1) has been
de-
is the
on the nature of the substrate
displayed
derivatives
and selenocarbonate
conditions.
trialkylstannanes
with
Each of these reactions
l.9,‘o
Scheme I Y R -_O-g-_H (4) Y R-O-L-X
R’ MH
R-H+M’
(I)
(5)
YM /
R-0-L
. (3)
Y=O We postulated the intermediate of cyclic systems with fi-elimination
or S;X=
Cl, OR’,
that, provided
a multiple
free-radical would
SR’,SeR:or bond is properly
(2) or (3) will undergo
require
that the annulation
of the intermediate
radical
Imidazalide; positioned
intramolecular efficiently
addition. compete
(3).”
641
M=R’;
Sn or Rq Si
on the residue
R of the carbonic
The suitability
of such a process for the construction
with hydrogen
abstraction
leading
acid derivative
to compounds
(l),
(4) or
642
We now report on the successful pounds
of type (1) were prepared
presence
of boron trifluoride
chloroformates
(6)
dithiocarbonate
and
application
of this new methodology
by known procedures
etherate
afforded
subsequently
(Scheme
the corresponding
(PhSeH,
pyridine)
(10) (R’ = R* = H; R3= Ph) was obtained
II).
for the synthesis
Treatment
3-alkyn-1-01s
into
the
of oxiranes
of a-alkylidene-y-lactones.
Com-
(6) with lithium
in the
(7),12 which were converted
corresponding
from the corresponding
acetylides
(phosgene)
phenylselenocarbonates
alcohol,
into the
(9).5
The
CS, and Mel.2b
Scheme II
R* o-
RI
c
0 (6)
(8)
X=CI
(9)
X=PhSe
(II 1
Ph s
I Ill
!-Shale
cb (IO)
The table displays
data on the free-radical
radical source, tri-n-butylstannane the cyclization sponding
of chloroformates
lactones
was practically
In a typical
experiment
were simultaneously mmol)
in
added,
benzene
(60
excess
ml).
The
duced by n-Bu,SnH
(13).
crude
(quantitative;
followed
cyclic
transformation
with Ph,SnH. ‘5 Presumably Ill.
of the selenocarbonates
(IO ml each) of n-Bu,SnH
of the acetylenic obtained
after
by fractionation
(10) took a different
of homopropargylic
added (1.5-3 h) to the substrates
yields were very high (entries
nmr, tic) and tin derivatives.
and the isolated
as shown in Scheme
solutions
solution
product,
acetate),
A similar
acid derivatives
was gradually
yield (entry a), the conversion
benzene
2 h, to a boiling
of n-Bu,SnH,
of carbonic
(nmr, tic) and their isolated
(entry b) individual
of the dithiocarbonate
benzylidenethionolactone thiocarbonylimidazolide
in moderate
quantitative
(silica gel; hexane-ethyl
The reaction a three-fold
occurred
during
(E)-a-benzylidene-y-butyrolactone chromatography
cyclization
and AIBN (azaisobutyronitrile),
of
acetonitrile
course (entry f). Full consumption
product
formed
into the corre-
(9) (R’ =R’=H; the
solvent,
by Angoh
and Clive
benzylidenethionolactone
R3=Ph)
(0.6
consisted
of
(67%) by flash
and hexane. of the starting
was found to be the benzylthionolactone
was observed
the initially
While
b-e).
The pure lactone’3,14 was obtained between
The
(6)-(10).
(0.9 mmol) and AIBN (0.085 mmol)
selenocarbonate evaporation
alcohols.
material
required
(14) rather than the
on treatment is further,
of an acetylenic and rapidly,
re-
643
Table: The Reaction of Homopropargylic
Derivatives
of Carbonic Acids (8)~(10) with Tri-n-butylstannane
and AIBN in Boiling
Benzene
Compounds
Products
*
Yield**
type (8)-(IO)
E/i**
%
Ph
Ph &’ cl
A
,.+
56
E
0
87
E
90
5/l
80
I A2
92
l/IO
0
Ph
,Ph .’
Se Ph
C
a
0
0
0 05
O&
0
d
,+ e
,Si
Me3
Se Ph
&O
4 f
Ph
,Ph
‘1
SMe
0
Ok
* See reference
S
0
14.
** Based on isolated
compounds
49
644
Scheme
III
Ph .
\I/
h
Sn
\s/ 0
(13)
Bus SnH
CH,Ol S
(14) References 1.
Review:
2.
a) Barton, D.H.R.; McCombie, S.W. J. Chem. Sot., Perkin Stange. A. Synthesis 1981, 743.
Hartwig,
W. Tetrahedron
Trans 7 1975, 1574.
3.
Robins, M.J.; Wilson, J.S.; Hansske,
1983, 105, 4059.
4.
Prisbe,
E.J.; Martin,
5.
Pfenninger.
6.
Kuivila,
1983, 39, 2609.
J.C. Synthetic
J.; Heuberger,
F. J. Am. Chem. Sot. Commun.
D.H.R.; Motherwell,
W.B.;
1985, 15, 401.
C.; Graf, W. He/v. Chim. Acta.
H.G.; Walsh, E.J. Jr. J. Am. Chem. Sot.
Beak, P.; Moje, S.W. J. Org. Chem., 1974, 39, 1320.
8.
Jackson,
F. J. Chem. Sot. Perkin
1980. 63, 2328.
1986, 66, 571.
7.
R.A.; Malek,
b) Barton,
Trans 7 1980, 1207.
9.
Barton,
D.H.R.; Crich, D.; Ltibberding,
10.
Barker,
P.J.; Beckwith,
11.
Reviews on free-radical cyclizations: a)Hart, D.J. Science 1984, 223, 883. b) Surzur, J.-M. in “Reactive Intermediates”, Abramovitch, R.A. Ed., Vol. 2, p.121, Plenum Press, New York and London, 1982. c) Beckwith, A..L.J. Tetrahedron 1981. 37, 3073.
12. Yamaguchi,
M.; Hirao, I. Tetrahedron
13.
For other preparations
14.
All compounds
15. Angoh,
A.; Zard, S.Z. J. Chem. Sot.,
A.L.J.. J. Chem. Sot., Chem. Commun.
Lett.
of (9) (R’ =R’=H;
gave analytical
R3=Ph)
and spectral
in UK 22 November
1985, 646.
1983, 24, 391. see Murray,
data consistent
A.G.; Clive. D.L.J. J. Chem. Sot., Chem. Commun.
(Received
Chem. Commun.
1984, 883.
1985)
A.W.; Reid, R.G. Syfithesis
with the assigned 1985, 980.
structure
1985, 35. and stereochemistry.
SYNTHESIS OF a-ALKYLIDENE-y-LACTONES ADDITION OF ALKOXYCARBONYL
BY INTRAMOLECULAR
FREE-RADICALS
Mario D. Bachi’
0040-4039/86 $3.00 + .OO 01986 Pergamon Press Ltd.
TO ACETYLENES
and Eric Bosch
Department of Organic Chemistry, The Weizmann lnstitote of Science, Rehovot, Israel
Abstract:a-Alkylidene-y-lactones rivatives of homopropargylic The free-radical deoxygenation dithiocarbonates2 desoxy formyl
products
of
reductive
most
of various useful,
thiocarbonylimidazolides,* (5).
Similar
ester (4) and/or
seems to follow
degradation The
alcohols.’
are obtained by treatment of chloroformate alcohols with tri-n-butylstannane.
reductions
alkanes
carbonic the
of chloroformates
acid
preparative
thionocarbonates,3,4
(5) depending
one of the mechanisms
on
scale,
extensively
and selenocarbonates.’
which
lead to the corresponding
or trialkylsilanes’
afford the corresponding
and the reaction
of
used for the
reaction
with trialkylstannane6,7
in Scheme
(1) has been
de-
is the
on the nature of the substrate
displayed
derivatives
and selenocarbonate
conditions.
trialkylstannanes
with
Each of these reactions
l.9,‘o
Scheme I Y R -_O-g-_H (4) Y R-O-L-X
R’ MH
R-H+M’
(I)
(5)
YM /
R-0-L
. (3)
Y=O We postulated the intermediate of cyclic systems with fi-elimination
or S;X=
Cl, OR’,
that, provided
a multiple
free-radical would
SR’,SeR:or bond is properly
(2) or (3) will undergo
require
that the annulation
of the intermediate
radical
Imidazalide; positioned
intramolecular efficiently
addition. compete
(3).”
641
M=R’;
Sn or Rq Si
on the residue
R of the carbonic
The suitability
of such a process for the construction
with hydrogen
abstraction
leading
acid derivative
to compounds
(l),
(4) or
642
We now report on the successful pounds
of type (1) were prepared
presence
of boron trifluoride
chloroformates
(6)
dithiocarbonate
and
application
of this new methodology
by known procedures
etherate
afforded
subsequently
(Scheme
the corresponding
(PhSeH,
pyridine)
(10) (R’ = R* = H; R3= Ph) was obtained
II).
for the synthesis
Treatment
3-alkyn-1-01s
into
the
of oxiranes
of a-alkylidene-y-lactones.
Com-
(6) with lithium
in the
(7),12 which were converted
corresponding
from the corresponding
acetylides
(phosgene)
phenylselenocarbonates
alcohol,
into the
(9).5
The
CS, and Mel.2b
Scheme II
R* o-
RI
c
0 (6)
(8)
X=CI
(9)
X=PhSe
(II 1
Ph s
I Ill
!-Shale
cb (IO)
The table displays
data on the free-radical
radical source, tri-n-butylstannane the cyclization sponding
of chloroformates
lactones
was practically
In a typical
experiment
were simultaneously mmol)
in
added,
benzene
(60
excess
ml).
The
duced by n-Bu,SnH
(13).
crude
(quantitative;
followed
cyclic
transformation
with Ph,SnH. ‘5 Presumably Ill.
of the selenocarbonates
(IO ml each) of n-Bu,SnH
of the acetylenic obtained
after
by fractionation
(10) took a different
of homopropargylic
added (1.5-3 h) to the substrates
yields were very high (entries
nmr, tic) and tin derivatives.
and the isolated
as shown in Scheme
solutions
solution
product,
acetate),
A similar
acid derivatives
was gradually
yield (entry a), the conversion
benzene
2 h, to a boiling
of n-Bu,SnH,
of carbonic
(nmr, tic) and their isolated
(entry b) individual
of the dithiocarbonate
benzylidenethionolactone thiocarbonylimidazolide
in moderate
quantitative
(silica gel; hexane-ethyl
The reaction a three-fold
occurred
during
(E)-a-benzylidene-y-butyrolactone chromatography
cyclization
and AIBN (azaisobutyronitrile),
of
acetonitrile
course (entry f). Full consumption
product
formed
into the corre-
(9) (R’ =R’=H; the
solvent,
by Angoh
and Clive
benzylidenethionolactone
R3=Ph)
(0.6
consisted
of
(67%) by flash
and hexane. of the starting
was found to be the benzylthionolactone
was observed
the initially
While
b-e).
The pure lactone’3,14 was obtained between
The
(6)-(10).
(0.9 mmol) and AIBN (0.085 mmol)
selenocarbonate evaporation
alcohols.
material
required
(14) rather than the
on treatment is further,
of an acetylenic and rapidly,
re-
643
Table: The Reaction of Homopropargylic
Derivatives
of Carbonic Acids (8)~(10) with Tri-n-butylstannane
and AIBN in Boiling
Benzene
Compounds
Products
*
Yield**
type (8)-(IO)
E/i**
%
Ph
Ph &’ cl
A
,.+
56
E
0
87
E
90
5/l
80
I A2
92
l/IO
0
Ph
,Ph .’
Se Ph
C
a
0
0
0 05
O&
0
d
,+ e
,Si
Me3
Se Ph
&O
4 f
Ph
,Ph
‘1
SMe
0
Ok
* See reference
S
0
14.
** Based on isolated
compounds
49
644
Scheme
III
Ph .
\I/
h
Sn
\s/ 0
(13)
Bus SnH
CH,Ol S
(14) References 1.
Review:
2.
a) Barton, D.H.R.; McCombie, S.W. J. Chem. Sot., Perkin Stange. A. Synthesis 1981, 743.
Hartwig,
W. Tetrahedron
Trans 7 1975, 1574.
3.
Robins, M.J.; Wilson, J.S.; Hansske,
1983, 105, 4059.
4.
Prisbe,
E.J.; Martin,
5.
Pfenninger.
6.
Kuivila,
1983, 39, 2609.
J.C. Synthetic
J.; Heuberger,
F. J. Am. Chem. Sot. Commun.
D.H.R.; Motherwell,
W.B.;
1985, 15, 401.
C.; Graf, W. He/v. Chim. Acta.
H.G.; Walsh, E.J. Jr. J. Am. Chem. Sot.
Beak, P.; Moje, S.W. J. Org. Chem., 1974, 39, 1320.
8.
Jackson,
F. J. Chem. Sot. Perkin
1980. 63, 2328.
1986, 66, 571.
7.
R.A.; Malek,
b) Barton,
Trans 7 1980, 1207.
9.
Barton,
D.H.R.; Crich, D.; Ltibberding,
10.
Barker,
P.J.; Beckwith,
11.
Reviews on free-radical cyclizations: a)Hart, D.J. Science 1984, 223, 883. b) Surzur, J.-M. in “Reactive Intermediates”, Abramovitch, R.A. Ed., Vol. 2, p.121, Plenum Press, New York and London, 1982. c) Beckwith, A..L.J. Tetrahedron 1981. 37, 3073.
12. Yamaguchi,
M.; Hirao, I. Tetrahedron
13.
For other preparations
14.
All compounds
15. Angoh,
A.; Zard, S.Z. J. Chem. Sot.,
A.L.J.. J. Chem. Sot., Chem. Commun.
Lett.
of (9) (R’ =R’=H;
gave analytical
R3=Ph)
and spectral
in UK 22 November
1985, 646.
1983, 24, 391. see Murray,
data consistent
A.G.; Clive. D.L.J. J. Chem. Sot., Chem. Commun.
(Received
Chem. Commun.
1984, 883.
1985)
A.W.; Reid, R.G. Syfithesis
with the assigned 1985, 980.
structure
1985, 35. and stereochemistry.