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Isothiocyanates of Natural Derivation.

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C O N F E R E N C E REPORTS
IJnder solvolytic conditions, ( 4 ) gives (5) [I],whereas (6)
does not rearrange to the anticipated 7-norborneol.
Isothiocyanates of Natural Derivation
A . K j e r , Copenhagen (Denmark)
The isothiccyanate-producing glucosidei form a unique and
interesting class of natural compounds. Besides the classical
representhttves,. sac!! a s siaigrin (1) and sinalbi.~.,t-h.i.s sk+s
now comprises about 45 gliicosides of the same general structure but possessing different side-chains. These can be saturated and unsaturated aliphatic, unbranched m-methylthioalkyl, unbranched keto-substituted alkyl, aralkyl, aryl,
heterocyclic, or p- or y-hydroxylated alkyl groups.
N -0SO3K
I1
(1)
Glucose-S-C-CH2-CH-CHz
The mass-spectra of about 50 individual isothiocyanates,
mainly of natural origin, were discussed. Unbranched aliphatic derivatives gave prominent peaks at m/e = 72, attributable to the ion CH*NCS+ produced by simple $-fission.
Strong peaks at m/e = 115 and M-33 obtained with isothiocyanates containing six or more carbon atoms were shown to
originate from intramolecular rearrangements. In all methylthioalkyl-substituted derivatives, a strong peak at m/e =
61 was observed due to the ion CH~SCHZ'..
The combination of vapor-phase chromatography and mass spectrometry
has proved extremely useful for the rapid and unequivocal
identification of small amounts of isothiocyanates of natural
origin.
[GDCh-Ortsverband Bonn (Germany), December 12th, 19631
[VB 781/117 IE]
(4)
r=JCH*-
M . Htrtinclc, Tubingen (Germany)
CH2-OK5
I,
In connection with the formation of ( 2 ) , the addition of a
methylene group onto the double bond of unsaturated cyclic alcohols by treating them with CHzI2 according to Simmons was investigated further. Cyclopropane compounds are
only formed if the OH group lies on a carbon atom adjacent
to the double bond or if the molecule can assume a conforniatioii in which the OH group comes into the proximity of
the double bond.
[GDCh-Ortsverband Wuppertal-Hagen at W uppertalElberfeld (Germany), December 1 Ith, 19631
[VB 779/121 IE]
German version: Angew. Chem. 76, 235 (1964)
Rearrangement of Vinylogous Carbonyl Chlorides
A . Roedig, Wurzburg (Germany) [2]
German version: Angew. Chem. 76, 276 (1964)
Investigations on Cyclopropane Compounds
(5)
Perchloropentadienal ( I o) [3], perchlorobutadienyl alkyl
ketones, e.g. ( I b), and perchlorobutadienyl aryl ketones,
e.g. f i e ) , which can be considered as vinylogues of Carbon$
chlorides, are converted irreversibly and quantitatively into
the isomeric acid chlorides when heated.
As was already shown previously, cyclopropyl carbinols of
the general structure
c1
c1
I
I
cl-c'c\'c-cl
" A
'
c 1 11
R-C-
cl;c
OH
cl-yC'c-Cl
d
Cl-C,\
o,,C-R
(1 )
react smoothly with acids and thereby. undergo homoallyl
rearrangement to the homoallyl halides. If two cyclopropane
rings are present in the molecule, the rearrangement proceeds with opening of the substituted cyclopropane ring only.
I n contrast, halogeno-substituted cyclopropyl carbinols, e..?.
2 - fluoro - 1 - cyclopropylethanol, no longer undergo normal
homoallyl rearrangement. The fluoro compound is readily
obtainable from cyclopropyl diazo ketone via the fluoromethy1 cyclopropyl ketone and rearranges with acids to cyclobutane compounds with elimination of fluorine.
The preparative and kinetic aspects of the formation of
cyclopropyl carbinols from homoallyl compounds was studied
jn several solvents. In weakly nucleophilic solvents, the cyclopropyl carbinyl compound is formed almost quantitatively.
The stability of the isomeric carbonium ions that are produced govern the composition of the products formed by
cycliration reactions: for example, ( I ) gives 70 :((2), whereas under the same conditions (3) does not isomerire to a
cyclopropane compound.
I120;l),"xan
(a!: R = H;
(b): R = CH,;
0
1' c 1
CCR
(2)
(r): R
= C6H:;
id): V
= CI
Starting from ( I ( ! ) labelled with radiocarbon at C-5, it was
shown that the oxygen atom and a 8-chlorine atom change
places during the rearrangement. Radioactive ( I 0) can be
quantitatively converted into radioactive (20) by heating it
for three hours in boiling CCI4. Hydrolysis of the acid chloride, thermal cyclization of the resultant acid to 3,4.5-trichloro-2-pyrone, and decarboxylative Diels-Alder condensation of this with maleic anhydride gives a diene adduct containing all the radioactivity ; none is found in the CO?;.
The rearrangement of ( I n ) is a first oder reaction, and its
rate is practically independent of the dielectric constant of
the solvent. Radical formers and radical scavengers have no
effect. The activation energy (22.8 kcal/mole) and activation
entropy (8-1 1 cal/deg/mole) are independent of the solvent;
the latter is negative.
The results indicate a mechanism involving a cyclic intermediate or transition state but do not show whether the
rearrangement proceeds via tetrachloropyran (30) (which
~
[ I ] B. D. Bartlett and S. Bank, J. Amer. chem. SOC.83, 2591
(1961); R . G. L a ~ t o n ibid.
,
83, 2399 (1961).
[2] Work carried out i n conjunction with R . Kohlhniipr, G. Miirk/,
G. Rohke, IY. Rnch, and M . Schlosser.
[3] A . Rordig and G . Miirk/, Liebigs Ann. Chem. 65Y, 1 (1962).
A i i g e w . Chem. internot. Edi?. / Voi. 3 (1964)
/
No. 4
317
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