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Conversion of Cyclic Nitrones to Thiolactams by Reaction with Carbon Disulfide.

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Conversion of Cyclic Nitrones to Thiolactams
by Reaction with Carbon Disulfide
By David St. Clair Black and Keith G. Watson"'
We report that the cyclic aldonitrones ( I a ) -( 1 c) ['I are
converted into the related thiolactams ( 3 a )-( 3 c ) , simply
by heating under reflux in carbon disulfide. The conversion
is spectroscopically quantitative and the pure thiolactams
can be isolated easily in high yields. The reaction presumably depends upon the loss of carbon oxysulfide from the
intermediates ( 2 ) , which are the expected products of the
cycloaddition of carbon disulfide to the nitrones ( I ) . A
similar reactionfz1involves loss of sulfur dioxide from the
cycloadduct of a nitrone and N-sulfinylaniline ; related
fragmentation reaction^'^.^] often occur if aromatic products can be formed.
We have been unable to detect the presence of the cycloadducts (2),even though reactions can be followed carefully by nuclear magnetic resonance spectroscopy. The
previously unknown thiolactams 5,5-dimethylpyrrolidine2-thione (3a), 3,3,5,5-tetramethylpyrrolidine-2-thione(3b),
and 5,5-dimethyl-4-phenylpyrrolidine-2-thione
(Jc) have
been characterized fully.
We have also observed that the C-phenyl nitrone ( 4 b )
undergoes thermal rearrangement and decomposition in
preference to any reaction with carbon disulfide.
Thus the conversion of aldonitrones to thioamides does
not hold for all nitrones and appears to require a nitrone
configuration which allows a reasonable rate"] of cycloaddition.
The Willgerodt-Kindler reactionfs1 already provides a
method for the conversion of simple aldehydes into thioamides, but is not readily applicable to the preparation of
thiolactams. The method described in this communication
compares very favorably with the main existing alternative,
which is the reaction'" of a lactam with phosphorus pentasulfide.
Received: September 3,1971 [Z 522 IE]
German version: Angew. Chem. 84,34 (1972)
Cycloaddition of Isocyanides to 4,5-Dihydro-l,3,5oxazaphosph(v)oles['*][
By Klaus Burger and Josef Fehn"'
We recently reported [I3+ 2lcycloadditions of 4,5-dihydro1,3,5-oxazaphosph(v)oles
to alkynes and alkenesf3!
We have now found an example of the very rare [3 + I]cycloaddition typeE4': Compounds ( I ) react with isocyanides in boiling benzene with elimination of phosphoric
acid esters to give 1:l adducts to which we ascribe the
structures of substituted azetines (2) on the basis of
spectroscopic data. The reaction could involve a nitrile
ylide intermediate.
( a ) , R' = R2 = H
( h ) , R' = H, R2 = CH,
(e), R' = c ~ H ~R~
, = H
Reports of cycloaddition reactions between carbon disulfide and nitrones or N-oxides are rare. In one special
casef5],a stable adduct is reported. On the other hand, isoquinoline N-oxider4' and the diphenyl nitrone ( 4 ~ ) are
' ~ ~
deoxygenated, supposedly via their respective cycloadducts.
This competing deoxygenation reaction is apparently
successful when it can afford a highly conjugated product.
(4a), R'
(4b), R'
R2 = C,H,
= C(CH,),;
R2 = C,H,
Groups R
R ' =C(CH,),
R3 = C 6 H ,
M.p. ( ' C )
B. p. ( C/torr)
Y~cld IR (cm-')
1705, 1645 [a]
1705,1645 [a]
1705 [b]
1700, 1630 [a]
Recorded [a] as films, [b] in KBr with a Perkin-Elmer Infracord.
[*] Dr. D. St. C. Black and Mr. K. G. Watson
Department of Chemistry, Monash University,
Clayton, Victoria. 3168 (Australia)
[I] R. Bonnetr, R. F. C . Brown, V M . Clark, 1.0.Sutherland,and A . Todd,
J Chem. SOC.1959, 2094; J . B. Bapar and D. St. C . Black, Austral. J.
Chem. 21, 2483 (1968).
[2] 0. Tsuge, M . Tashiro, and S. Mataka, Tetrahedron Lett. 1968,3877.
[3] R. Huisgen, Angew. Chem. 75,604 (1963); Angew. Chem. internat.
Edit. 2, 565 (1963).
[4] H . Seidl, R. Huisgen, and R. Grashey, Chem. Ber. 102, 926 (1969).
[5] 7: Sasaki and M . Ando, Bull. Chem. SOC.Japan 41,2960 (1968).
[6] M . Harnana, B. Umezawa, and S. Nakashima, Chem. Pharmac.
Bull. (Tokyo) 10,969 (1962).
[7] R. Huisgen, H.Seid/, and I . Briining, Chem. Ber. 102, 1102 (1969).
[8] R. Guhprt, R. Piganiol, A . Carayon-Gentil, and P. Chabrier, Bull
SOC. Chim. France 1965,224.
[9] W Walter and K . D. Bode, Angew. Chem 78, 517 (1966); Angew.
Chem. internat. Edit. 5,447 (1966).
Angew. Chem. infernal. Edit.1 Vol. I 1 (1972)
No. 1
Supporting evidence for structure (2) comes from the
acid hydrolysis of (2c) to phenylglyoxylic acid as well as
from the hydrogenation of the endocyclic double bond
of (2c) with LiAlH, and acid hydrolysis of the resulting
azetidine to N-(2,2,2-trifluoro-1-trifluoromethylethyl)phenylglycine cyclohexylamide.
2-Alkyl- and 2-aryl-I-azetines have become accessible
only very recently by pyrolysis of cyclopr~pylazides'~~;
hitherto only a few 2-alkoxy-, 2-alkyIthio-, and 2-chloro-lazetines derived from p-lactams were known'".
[*] Dr. K. Burger and Dip].-Chem. J. Fehn
Organisch-chemisches Institut der Technischen Universitat
8 Miinchen 2, Arcisstrasse 21 (Germany)
[**I This work was supported by the Deutsche Forschungsgemeinschaft.
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nitrone, thiolactams, cyclic, reaction, carbon, disulfide, conversion
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