Thiofenchone S-methylide and its spiro-1,3,4-thiadiazoline precursor

Article abstract of DOI:10.1002/hc.1022

Spiro[fenchane-2,2′-(1,3,4)-thiadiazoline] (6), prepared from thiofenchone and diazomethane, extrudes N₂(t_1/2 22 min, 46°C, toluene) and furnishes the S-methylide 7 which, in turn, closes the thiirane ring or else is intercepted by 1,3-cycloadditions to dipolarophiles (tetracyanoethylene, maleic anhydride, N-methyl-1,2,4-triazoline-3,5-dione, aromatic thioketones). When thiocarbonyl S-methylide 7 is set free in methanol, fenchone S,O-dimethylacetal is formed as an HX adduct. Catalysis by acetic acid converts 7 to 1-(methylthio)-α-fenchene (25) by way of a Wagner-Meerwein rearrangement. The addition of diazomethane to thiocampher leads, via thiadiazoline 12, to thiocamphor S-methylide; the latter undergoes a 1,4-H shift, thus affording 2-methylthio-2-bornene (11).

Full text of DOI:10.1002/hc.1022

Heteroatom Chemistry
Volume 12, Number 3, 2001
Thiofenchone S-Methylide and Its Spiro-1,3,4-
thiadiazoline Precursor
Rolf Huisgen, Grzegorz Mloston, and Albert Pro¨bstl
Department Chemie, Ludwig-Maximilians-Universita¨t Mu¨ nchen Butenandtstr. 5—13 (Haus F),
D-81377 Mu¨ nchen, Germany
Received 30 October 2000
pounds, and thermal N2 extrusion furnishes thioke-
tone S-alkylides, which can be intercepted in situ.
Cycloadditions of diazomethane to dialkylthio-
ketones afford the regioisomers 1 and 2 [2]. The
higher the branching of the alkyl groups, the larger
is the fraction of the 2,5-dihydro-1,3,4-thiadiazoles
2, which suggests a steric effect. In this process, in-
creasing solvent polarity favors 1. Consideration of
the dipole moments of thione and diazomethane
supports a higher polarity of the transition state (TS)
leading to 1. This energetic disadvantage is mitigated
by the use of polar solvents (Scheme 1).
The same interplay of forces is observed in dia-
zomethane additions to cycloalkanethiones. Ada-
mantanethione (3) afforded thiadiazolines of types 1
and 2 in a ratio of 9:91 in pentane, and 90:10 was
ABSTRACT: Spiro[fenchane-2,2Ј-(1,3,4)-thiadiazo-
line] (6), prepared from thiofenchone and diazome-
thane, extrudes N2 (t1/2 22 min, 46ЊC, toluene) and fur-
nishes the S-methylide 7 which, in turn, closes the
thiirane ring or else is intercepted by 1,3-cycloaddi-
tions to dipolarophiles (tetracyanoethylene, maleic an-
hydride, N-methyl-1,2,4-triazoline-3,5-dione, aro-
matic thioketones). When thiocarbonyl S-methylide 7
is set free in methanol, fenchone S,O-dimethylacetal is
formed as an HX adduct. Catalysis by acetic acid con-
verts 7 to 1-(methylthio)-␣-fenchene (25) by way of a
Wagner-Meerwein rearrangement. The addition of dia-
zomethane to thiocampher leads, via thiadiazoline 12,
to thiocamphor S-methylide; the latter undergoes a
1,4-H shift, thus affording 2-methylthio-2-bornene
(11). ᭧ 2001 John Wiley & Sons, Inc. Heteroatom
Chem 12:136–145, 2001
observed in methanol, both at מ30ЊC [3,4].
Ab initio calculations (RHF/6-21G*, CAS(6,5)//3-
21G*) of the TS confirm the concerted pathway of
INTRODUCTION
The 1,3-cycloadditions of thiocarbonyl ylides with
C–C multiple bonds and hetero-double bonds offer a
versatile route to five-membered S-heterocycles [1].
2,5-Dihydro-1,3,4-thiadiazoles are formed by cy-
cloaddition of diazoalkanes to thiocarbonyl com-
Correspondence to: Rolf Huisgen.
Contract Grant Sponsor: Fonds der Chemischen Industrie.
Dedicated to Professor Richard Neidlein, Heidelberg, on the oc-
casion of his 70th birthday.
1,3-Dipolar Cycloadditions, 120. For part 119 see Finke, J. A.;
Huisgen, R., Temme, R. Helv Chim Acta, 2000, 83, 3333.
᭧ 2001 John Wiley & Sons, Inc.
SCHEME 1
136

Thiofenchone S-Methylide and Its Spiro-1,3,4-thiadiazoline Precursor 137
these diazomethane cycloadditions, as well as simi-
lar activation enthalpies for both directions of ad-
dition [5]. The low-lying LUs of thiones contribute
weight to the HO(diazomethane)-LU(thione) inter-
action and promote our understanding of the super-
dipolarophilic character of thiones [6].
The cycloadditions of thiocarbonyl ylides 4 to
cis,trans-isomeric dipolarophiles are usually stereo-
specific. However, strong steric hindrance at one ter-
minus can change the mechanism from the con-
certed to a two-step pathway via a zwitterionic
intermediate [7]. We report here on thiofenchone S-
methylide (7) [8] in which the 1,3-dipolar system is
more encumbered than in adamantanethione S-
methylide (42).
elimination of N2 from 6 obeys the first-order law;
the half-life in toluene amounts to 22.2 minutes at
1
46ЊC and to 16.5 minutes at 52ЊC. H NMR analysis
with weight standard indicated 63% of spirothiirane
8 and a diastereoisomer ratio of 60:40. We do not
regard the small dH differences of the methyl signals
[9] as a reliable basis for an endo/exo assignment.
The generation of two diastereoisomers of 8
from one and the same thiadiazoline 6 would be in-
consistent with a concerted formation of the new C–
C bond. During the extrusion of N2, the group C(2)–
S–CH2 swings into a quasi-plane: The thiofenchone
S-methylide (7) occurs as an interceptible interme-
diate. Both syn- and anti-conformations are conceiv-
able, and both can give rise to 8a and 8b by another
set of conrotatory 90ЊC rotations about the C–S
bonds.
SPIRO-1,3,4-THIADIAZOLINES OF
FENCHANE AND CAMPHANE SERIES
Thiocamphor (9) can tautomerize with
a
thioenol, in contrast to thiofenchone (5). A methyl-
ation of the acidic thioenol 10 by diazomethane ap-
peared plausible, and indeed we obtained 2-(meth-
ylthio)-2-bornene (11) from the reaction at room
temperature. However, when 9 and diazomethane
The reaction of thiofenchone (5) with diazomethane
at 0ЊC was described by Beiner et al. in 1973; Gas
chromatography (GC) analysis of the oily product in-
dicated 50% of the spirothiirane 8 with an endo/exo
ratio of 65:35 [9]. The question of the reaction path-
way was left open.
Our supposition that 5, like other sterically hin-
dered thiones, should add diazomethane to afford a
type 2 thiadiazoline, turned out to be correct. The
reaction in tetrahydrofuran (THF) at 0ЊC produced
1
reacted at מ40ЊC and reached 10ЊC, the H NMR
spectrum showed the 1,3,4-thiadiazoline 12 and
thioenol ether 11 side by side; the two sets of C-
methyl singlets suggested a 1:1 ratio. After 4 hours
1
at room temperature, H NMR showed 82% of 11,
while the signals of 12 had disappeared (Scheme 3).
Compound 12 was confirmed by its 1H NMR pa-
rameters. The observed AB spectrum at d 5.45 and
5.89 with Jgem ס 16.8 Hz is consistent with 5Ј-H2 of
12; the 5Ј-H2 of 6 resonates at d 5.55 (as A2 spectrum).
The properties of 11 agree with those described by
Dagonneau et al. for the product from 9 and methyl
magnesium bromide [12]. The vinylic 3-H appears
as a doublet at d 5.38.
a
sterically homogeneous spiro[fenchane-2,2Ј-
1
(1,3,4)-thiadiazoline], as the H NMR spectrum of
the crude adduct revealed. On the other hand, as-
signment of the endo-structure 6 is merely based on
the following analogy: The reduction of fenchone
with LiAlH4 produced ␣-fenchol (endo-OH) and b-
fenchol (exo-OH) in a ratio of 97:3 [10,11]; as a con-
sequence, we assume that diazomethane as well as
the hydride ion enter from the exo side. The crystal-
line 6 can be stored at מ25ЊC (Scheme 2).
Obviously, 12 extrudes N2 at 20ЊC, and the thio-
camphor S-methylide (13) favors a sigmatropic 1,4-
H shift as a route to stabilization. This reaction type
Kinetic measurements showed that the thermal
SCHEME 2
SCHEME 3

138 Huisgen, Mloston, and Pro¨bstl
is well documented [13,14] and is allowed to be con-
certed by orbital control. It is the counterpart of the
1,5-H shift of 1,3-dienes with adjacent C–H bond.
The 1,4-H shift of S-methylide 13 via a five-mem-
bered TS supersedes thiirane formation; indeed, no
thiirane was found.
nus, giving rise to the sulfonium ion 19 ם methan-
olate, followed by ion recombination (Scheme 5).
Liberation of the S-ylide 7 in the presence of 1
equiv. of acetic acid in THF (12 hours, 40ЊC) fur-
nished 1-(methylthio)-␣-fenchene (25), which is
formed by a Wagner-Meerwein rearrangement [17]
of the carbosulfonium ion 19. The yield of 25 was
52% by 1H NMR analysis and 44% by isolation. 2,2-
Bis(methylthio)fenchane (21) appeared as a by-
product (46%, based on 2 mol equiv. of 7), but is of
somewhat obscure provenance.
The vinyl protons of 25 appear at dH 4.83 and
5.12, whereas the CH3S group resonates at 2.07.
Chemical evidence came from the treatment of 25
with Raney nickel in refluxing ethanol. Beside the
hydrogenolysis of the C–S bonds, a saturation of the
CסC bond was observed. The products formed in
this process were endo- and exo-2,7,7-trimethylnor-
bornane (23 and 24), in the literature also known as
isobornylanes or ␣-fenchanes [18].
SPIROTHIADIAZOLINE 6 AS AN ACID
When 6 was treated with 1.0 equiv. of sodium meth-
anolate in methanol, the lack of N2 evolution at 45ЊC
signals complete conversion to the anion 14. The lat-
ter shares the propensity for 1,5-electrocyclic ring
opening with other thiadiazoline anions [15]. The
thioformimidate 16, obtained with 2,4-dinitrochlo-
robenzene, is derived from anion 15 (Scheme 4).
On the side, we mention the amidrazones 17 and
18 which were formed from 6 with piperidine or
morpholine at room temperature in a multistep re-
action: base-catalyzed equilibration of 6 with the
open-chain tautomer (N-protonated 15) and inter-
action of the latter with the sec-amine [16]. The
structures 16–18 were confirmed by their spectra.
An authentic sample of ␣-fenchene (26) was sub-
jected to the same hydrogenation with Raney nickel
and ethanol. The endo/exo mixtures of 23 and 24
were identified by their 13C signals (3q, 3t, 3d, 1s
each), and a statistical analysis revealed the endo/exo
ratios, 23/24, namely 68:32 for the product from 25,
and 61:39 for the reduction of 26. Since the deviation
exceeds the error limit, we conclude that the reduc-
THIOFENCHONE S-METHYLIDE AND ACIDS
As heteroatom derivatives of allyl anions, thiocar-
bonyl ylides are bases. When the N2 elimination from
thiadiazoline 6 took place in methanol at 45ЊC, fen-
chone O,S-dimethylacetal (20) was formed in 96%
yield. The conversion to fenchone 2,4-dinitrophen-
ylhydrazone attested to the unchanged carbon
framework. The homogeneity of 20 is remarkable;
the CH3O singlet appears at d 3.41 and that of CH3S
at 1.93. For analogy reasons, we suspect a structure
incorporating exo-OCH3 and endo-SCH3. The initial
step is probably protonation of 7 at the CH2 termi-
SCHEME 4
SCHEME 5

Thiofenchone S-Methylide and Its Spiro-1,3,4-thiadiazoline Precursor 139
tion of 25 does not completely take place via 26 as
an intermediate. It is noteworthy that the hydrogen-
ation of 26 with Pd/H2 in ethanol afforded 23 and 24
in the ratio of 29:71, that is, this time the exo-form
predominates. Brown and Kawakami studied the re-
duction of ␣-fenchene and observed 23/24 ס 14:86
for hydroboration/protonolysis and 27:73 for the Pt-
catalyzed hydrogenation [19]. The reduction of ␣-
fenchene, catalyzed by Rh(PPh)3Cl, gave 23/24 ס
63:37, according to Rousseau et al. [20].
We briefly touch the problem of endo/exo assign-
ment of 23 and 24, even though it is not essential in
our context. The hydroborations of bornene and
apobornene proceed exclusively from the endo side.
When the same procedure was applied to 2,7,7-tri-
methylnorbornene (27), it was concluded that the
major product must be that of endo-hydroboration:
23/24 ס 13:87 was found [19]. The connection with
our 13C NMR parameters stems from the near iden-
tical ratios of 23/24 observed in catalytic hydrogen-
ation, 27:73 for Pt/H2 [19], and 29:71 for Pd/H2 (this
work).
SCHEME 6
cycloadduct cannot be excluded. After the reaction
of 7 with N-methyl-1,2,4-triazolinedione, H NMR
1
Why is the reaction of 7 with methanol not ac-
companied by the carbonium rearrangement to give
25 (an isomer of 7), in contrast to the use of acetic
acid as a catalyst? Methanolate recombines very rap-
idly with the carbosulfonium ion 19, perhaps within
a contact ion pair. The acetate anion is less nucleo-
philic and allows 19 a sufficient lifetime for the re-
arrangement. 2-Methylpropane-2-thiolate is a steri-
cally hindered nucleophile. When 7 was set free from
6 in THF in the presence of 1.1 equiv. of tert-butyl
analysis established 54% of diastereoisomeric cy-
cloadducts 30 in a ratio of 55:45. Partial separation
was achieved by PLC, and moderate amounts of both
isomers were obtained pure. Base peak in the MS of
ם
ם
30A is m/z 168 for C10H16S (5 ), accompanied by
ם
ם
m/z 135 (40%) for C10H15; [M מ SH] is generally
found as a fragment of the cation radicals of thiok-
etones [21].
Surprisingly, the reaction of 6 (via 7) with 2
equiv. of thiobenzophenone (31) did not give rise to
the 1,3-dithiolane with spirofenchane group and two
phenyl substituents, but rather to 4,4,5,5-tetra-
phenyl-1,3-dithiolane (33, 86% yield). The latter
originates from addition of thiobenzophenone S-
methylide (34) with 31 [15]. The transfer of a CH2
group from 7 to 31, producing 34 ם 5, and subse-
quent addition of 34 to a second molecule of 31 is a
plausible pathway. Possibly, the transfer proceeds
through 32, which can be described as zwitterion or
biradical (Scheme 7).
We encountered this CH2 transfer in the reaction
of 34 with adamantanethione (3); in addition to the
expected cycloadduct, 8% of 33 was isolated [22].
The stronger the steric encumbrance of the thione
S-methylide, the more the methylene transfer to
thiobenzophenone becomes prevalent. For example,
the reaction of S-ylide 35 with excess of 31 gave 96%
of 33, and tetramethylindane-2-thione was set free
[23].
1
mercaptan, H NMR analysis established 59% of 1-
(methylthio)-␣-fenchene (25).
1,3-CYCLOADDITIONS OF THIOFENCHONE
S-METHYLIDE (7)
Thiocarbonyl ylides are nucleophilic 1,3-dipoles,
and electrophilic dipolarophiles are favored as cy-
cloaddition partners. When N2 was extruded from 6
in THF at 50ЊC in the presence of 1.2 equiv. of tetra-
cyanoethylene, two crystalline cycloadducts were
obtained and separated by preparative layer chro-
matography on silica gel (PLC). Quantitative 1H
NMR analysis indicated 59% and 29% of two stereo-
isomers 28a and 28b, the endo/exo assignment being
unknown. The 1H and 13C NMR parameters fit struc-
ture 28 (Scheme 6).
The reaction with maleic anhydride (1.2 equiv.)
provided a crystalline cycloadduct 29 (43%) and, in
addition, 27% of 25, the product of the Wagner-
Meerwein rearrangement. Supposedly, a trace of
maleic acid (hydrolysis of the anhydride) catalyzed
the isomerization 7 → 25. The presence of a second
When the S-ylide 7 (2.00 mmol) interacted with
thioxanthione (37) in THF at 40ЊC, 0.60 mmol of the
1,3-dithiolane 41 with two spiro-thioxanthene resi-
dues precipitated; the same compound was obtained

140 Huisgen, Mloston, and Pro¨bstl
SCHEME 7
by Scho¨nberg et al. from 37 and diazomethane [24]
1
(Scho¨nberg reaction [15]). H NMR analysis of the
soluble product showed 0.98 mmol of a mixture of
two 1:1 cycloadducts. We did not succeed in sepa-
rating them, but the similarity of the 1H NMR spec-
tra pointed to diastereoisomers of 36 with respect to
the fenchylidene group; their ratio, 85:15, was deter-
mined from the intensities of 13C signals. The AB
spectrum of 5Ј-H2 at d 3.53 and 3.84 of the major
cycloadduct did not distinguish between 36 and 40.
Clear evidence came from the C–S hydrogenolysis
with nickel in ethanol: the occurrence of fenchane
and 1,1-diphenylethane matched our expectation
concerning 36. The base peak in the MS is m/z 210
SCHEME 8
course cannot be applied. The implications will be
discussed elsewhere.
In conclusion: The cycloadditions of thiofen-
chone S-methylide (7) are hampered by severe steric
hindrance which reduces the yields. In several ex-
periments, substantial amounts of thiofenchone (5)
point to side reactions. Adamantanethione S-meth-
ylide (42) and thiobenzophenone S-methylide (34)
are certainly not free of steric screening of one of the
terminal C-atoms; nevertheless, they still participate
in the notoriously smooth course of 1,3-dipolar cy-
cloadditions and furnish high adduct yields with
electron-deficient dipolarophiles [26].
ם
(C14H10S ), which corresponds to [9-methylenexan-
ם
thione] . This is a general fragmentation path of 1,3-
dithiolanes [22,25] and accords with 36 (Scheme 8).
Since the 1,3-addition of adamantanethione S-
methylide (42) to 37 produced two regioisomeric di-
thiolanes [25], our tentative reaction scheme dis-
plays both regioisomers as well, 36 and 40. Due to
the proximity of the voluminous groups in the 4Ј-
and 5Ј-positions, 40 equilibrates with 38, and stabi-
lization is gained by formation of 41 via the splitting
products 5 ם 39 and renewed addition with 37. The
perpendicular arrangement of the thioxanthene res-
idues in 41 probably generates less van der Waals
pressure than the involvement of the fenchylidene
group does in 40. However, the mechanism of the
addition of thione S-methylides to thiones (one-step
or two-step) is not settled yet; the criterion of steric
EXPERIMENTAL
General [27].
2Ј,5Ј-Dihydrospiro[fenchane-2,2Ј-(1,3,4)-thiadi-
azole] (6) (1R,4S)-(מ)-Thiofenchone (5) [28]. For
purification on the 20 g scale, column chromatog-

Thiofenchone S-Methylide and Its Spiro-1,3,4-thiadiazoline Precursor 141
raphy on silica gel (200 g) with pentane was suitable.
1H NMR (CDCl3) d 1.12, 1.15, 1.28 (3s, 3 CH3), 1.52,
1.72 (2m, 6H, 3 CH2), 2.29 (m, 4-H).
achieved. 1H NMR (CDCl3, major/minor) d 0.82/0.80
(s, CH3), 0.92/0.85 (s, CH3); both isomers: 1.01 (s,
broadened, CH3), 1.15–2.10 (m, 3 CH2, 4-H), 2.36 (s,
broad, 3Ј-CH2). Anal. calcd for C11H18S (182.32): C,
72.46; H, 9.95; S, 17.59; found: C, 72.35; H, 10.08; S,
17.53.
Thiofenchone and Diazomethane. Compound 5
(840 mg, 5.00 mmol) was reacted with 20 mL of
0.475 M diazomethane (9.5 mmol, titrated content)
in absolute THF for 2 hours. Evaporation at 0ЊC/15
mm and, finally, at 0ЊC/0.01 mm left a colorless oil;
Fenchone Nb-[(2,4-Dinitrophenylthio)-
methylene]hydrazone (16)
1
the H NMR spectrum showed only the signals of
thiadiazoline 6. The oil crystallized at מ25ЊC, m.p.
66–67ЊC (dec., N2), and gave correct analyses without
further purification (yield nearly quantitative). Dis-
solving in ether and cooling to מ25ЊC afforded 6 as
colorless rods. 1H NMR (CDCl3) d 0.70 (s, CH3), 0.94
(s, 2 CH3), 1.53–1.82 (m, 3 CH2), 2.69 (d, 4-H), 5.55
(s, 5Ј-H2); (C6D6) d 0.45, 0.65, 0.70 (3s, 3 CH3), 1.00–
1.68 (m, 3 CH2), 2.49 (d, 4-H), 4.92 (s, 5Ј-H2). Anal.
calcd for C11H18N2S (210.34): C, 62.81; H, 8.63; N,
13.32; found: C, 62.64; H, 8.72; N, 12.84.
Compound 6 (420 mg, 2.00 mmol) in 20 mL of ab-
solute methanol was reacted with sodium methan-
olate (2.00 mmol); no N2 evolution was observed at
45ЊC. 2,4-Dinitrochlorobenzene (405 mg, 2.00
mmol) was slowly added, and the solution heated to
45ЊC for 30 minutes. Workup with H2O/CH2Cl2, PLC
(CH2Cl2), and recrystallization from isopropyl alco-
hol afforded 16 (420 mg, 56%) in golden-yellow nee-
dles, m.p. 72–73ЊC. IR (CHCl3) m 1346 vst, 1532 vst
1
(NO2); 1598 st, 1645 st (CסN). H NMR (CDCl3) d
Even simpler is the passing of gaseous diazo-
methane, diluted by N2, into the solution of 2.0 mmol
of 5 in 30 mL of diethyl ether at מ10ЊC, until the
orange color turns light-yellow; this procedure re-
quires some experience. Compound 6 crystallized
from pentane at מ78ЊC.
1.22, 1.25, 1.32 (3s, 3 CH3, 1.4–2.0 (m, 7 H), 7.75 (s,
HCסN), 7.80 (d, J ס 8.6 Hz, 6Ј-H), 8.55 (dd, J ס 8.6,
2.0 Hz, 5Ј-H), 8.82 (d, J ס 2.0 Hz, 3Ј-H). MS (90ЊC);
m/z (%) 376 (11) [M ], 81 (100) [C6H9 ]. Anal. calcd
for C17H20N4O4S (376.43): C, 54.24; H, 5.36; N, 14.89;
S, 8.52; found: C, 54.27; H, 5.37; N, 14.74; S, 8.82.
ם
ם
Kinetics of N2 Extrusion from 6. The magneti-
cally stirred solution of 5.0 mmol of 6 in 10 mL of
toluene was connected with a nitrometer (150 mL)
and heated in a bath of 46 ע 1ЊC. After 6 minutes
(22 mL of N2), constancy of the temperature was as-
sumed, and the N2 volumes were monitored; the
value after 180 minutes serving as Vϱ. The plot of log
(Vϱ/Vϱ מ Vt) vs. time (20 values) was linear (r ס
0.999) up to 90% reaction and provided 104 k2 ס 5.2
Fenchone Nb-(Piperidinomethylene)hydrazone
(17)
Compound 6 (2.00 mmol) in 10 mL of piperidine was
kept for 3 hours at room temperature and worked
up with H2O/CH2Cl2. PLC (CH2Cl2/ethanol 9:1) pro-
vided 17 (250 mg, 48%) as a colorless oil. IR (neat)
m 1105 m, 1209 st, 1258 st, 1453 st; 1609 vst, 1652 vst
1
(CסN). H NMR (CDCl3) d 0.90–1.87 (m, 15 H), su-
s
מ1. The total N2 volume (98%) was measured after
perimposed by 1.17, 1.22, 1.28 (3s, 3 CH3), 3.04–3.38
(m, CH2-N), 7.64 (s, HCסN). 13C NMR (CDCl3) d 17.6,
23.3, 24.0 (3q, 3 CH3), 24.8, 25.5 (2t, 2 CH2), 25.6 (t,
2 CH2), 34.4 (t, broadened, CH2), 43.2 (t, CH2), 47.2
(t, 2 N-CH2), 44.9, 50.3 (2s, C-1, C-3), 48.8 (d, C-4),
157.7 (d, NסCH–N), 177.3 (s, C-2). MS (30ЊC); m/z
cooling to room temperature. A second measure-
ment at 52 ע 1ЊC (18 values with r ס 0.999 up to
מ1
86% reaction) gave 104 k2 ס 7.0 s
.
Spiro[fenchane-2,2Ј-thiirane] (8)
ם
ם
ם
(%) 261 (72) [M ], 245 (9) [M -CH3], 233 (13) [M
ם
The combined solutions of the kinetic experiments
were freed of toluene in vacuo. The 1H NMR analysis
of the s at d 2.36 with trichloroethylene (d 6.70) as a
weight standard indicated 63% of 8, and an isomer
ratio of 60:40 was determined from the integrals at
d 0.92 and 0.85. Bulb-to-bulb distillation at 55–60ЊC/
10מ3 mm furnished 8 (47%) as a colorless oil, which
became glassy at 25ЊC and had a mintlike smell. Af-
ter preparative layer chromatography (PLC) (2 mm
silicagel, Merck PF254) with pentane, the isomer ratio
was unchanged, and crystallization was not
מ C2H4], 177 (30) [M מ NC5H10], 152 (45)
ם
ם
[C9H16C ס NH2 ], 111 (37), 84 (100) [NC5H10], 83
(62), 81 (31). Anal. calcd for C16H27N3 (261.40): C,
73.51; H, 10.41; N, 16.08; found: C, 73.57; H, 10.40;
N, 15.78.
Fenchone Nb-(Morpholinomethylene)hydrazone
(18)
The same procedure with 2.00 mmol of 6 and 10 mL
of morpholine furnished 220 mg (42%) of 18 as a

142 Huisgen, Mloston, and Pro¨bstl
colorless oil. IR (neat) m 869 st, 1116 vst (C-O), 1231
st, 1269 st, 1445 st, br.; 1605 vst, 1652 vst (CסN). 1H
NMR (CDCl3) d 0.9–2.13 (m, 7 H), superimposed by
1.23, 1.28, 1.32 (3s, 3 CH2), AAЈBBЈ at 3.19–3.45 (2
CH2-N), 3.54–3.81 (m, 2 CH2-O), 7.67 (s, CHסN). MS
methoxy-endo-2-(methylthio)fenchane (20, 130 mg,
61%), m.p. 126–128ЊC. IR (KBr) m 904 st, 926 st, 1069
vst, 1088 vst (C–O); 1473 st. 1H NMR (CDCl3) d 0.70–
2.22 (m, 7 H), superimposed by 1.10, 1.13, 1.15 (3s,
3 CH3), 1.93 (s, SCH3), 3.41 (s, OCH3). MS (30ЊC);
ם
ם
ם
ם
(30ЊC); m/z (%) 263 (92) [M ], 248 (7) [M -CH3], 247
m/z (%) 215 (3) [M ם 1], 199 (15) [M מ CH3], 183
ם
ם
ם
(11), 222 (8), 221 (6), 195 (7), 177 (100) [M -
(8) [M מ OCH3], 167 (88) [M מ SCH3], 152 (12)
[167 מ CH3], 131 (13), 123 (9), 93 (10), 81 (100)
ם
NC4H8O], 152 (36) [C10H18N ], 115 (29), 113 (42)
ם
ם
ם
[C5H9N2O , probably OC4H8N-CϵNH ], 91 (10)
[C6H9 ], 80 (13). Anal. calcd for C12H22OS (214.36): C,
ם
ם
ם
[C7H7 ], 86 (52) [OC4H8N ], 81 (45) [C6H9 ]. Anal.
calcd for C15H25N3O (263.37): C, 68.40; H, 9.57; N,
15.96; found: C, 68.21; H, 9.54; N, 15.76.
67.23; H, 10.26; S, 14.96; found: C, 66.92; H, 10.23;
S, 15.05.
Compound 20 (107 mg, 0.50 mmol) was reacted
with 2,4-DNPH in ethanolic H2SO4. After 2 days at
room temp., 145 mg (87%) of (מ)-fenchone 2,4-di-
nitrophenylhydrazone was filtered, m.p. 160–162ЊC,
identified by mixed m.p. and 1H NMR spectrum. 1H
NMR (CDCl3) d 1.32, 1.37, 1.45 (3s, 3 CH3), 1.2–2.1
(m, 7H), 7.82 (d, J ס 9.6 Hz, 6Ј-H), 8.20 (dd, J ס 9.6,
2.4 Hz, 5Ј-H), 9.00 (d, J ס 2.4 Hz, 3Ј-H).
2Ј,5Ј-Dihydrospiro[camphane-2,2Ј-(1.3.4)-
thiadiazole] (12)
Thiocamphor (9) and Diazomethane.
(ע)-9
[29], (500 mg, 2.97 mmol) was added to ϳ12 mmol
of diazomethane in 30 mL of ether at מ40ЊC. After
the solution reached 10ЊC in 2 hours, thin-layer chro-
matography (TLC) showed that 9 was consumed.
Ether and diazomethane were removed in vacuo at
0ЊC. The remaining colorless oil contained 11 and 12
in nearly 1:1 ratio, according to the six C–CH3 sin-
glets in the 1H NMR spectrum (CDCl3). After 4 hours
Acetic Acid. Compound 6 (841 mg, 4.00 mmol)
in 12 mL of abs. THF and 240 mg (4.00 mmol) of
acetic acid was heated at 40ЊC for 12 hours (96% N2).
1
After evaporation of the solvent, H NMR analysis
(CDCl3) with trichloroethylene showed 2.08 mmol
(52%) of 25 (s at d 4.83). PLC (petroleum ether/
CH2Cl2 9:1) furnished 210 mg, 0.91 mmol of 21 (46%,
based on 2 equiv. of 6) as the first fraction, followed
by 25 (320 mg, 44%). A second PLC procedure was
required to obtain 25 analytically pure.
1
at room temperature, H NMR analysis with 1,3,5-
trimethoxybenzene as weight standard (s at d 3.70,
6.05) indicated 82% of 11 (d at d 5.38).
2-(Methylthio)-2-bornene (11). IR (neat) m 1562
1
m (CסC). H NMR (CDCl3) d 0.78, 0.83, 1.00 (3s, 3
CH3), 1.0–2.1 (m, 2 CH2), 2.17 (s, SCH3), 2.34 (t, J ס
3.5 Hz, 4-H), 5.38 (d, J ס 3.5 Hz). Anal. calcd for
C11H18S (182.32): C, 72.46; H, 9.95; S, 17.59; found:
C, 72.89; H, 9.77; S, 17.27.
2,2-Bis(methylthio)fenchane (21).
21 was recrystallized from methanol at מ78ЊC, m.p.
117–119ЊC. IR (KBr) m 1105 m, 1346 m, 1386 m, 1459
Compound
1
st. H NMR (CDCl3) d 0.80–2.45 (m, 7 H), superim-
posed by 1.21 (s, 3-endo-CH3), 1.27 (s, 1-CH3, 3-exo-
CH3), 2.05 (s, endo-SCH3), 2.11 (s, exo-SCH3). MS
1H NMR of Thiadiazoline 12 (CDCl3, subtrac-
tion of signals of 11) d 0.67, 0.93, 1.04 (3s, 3 CH3),
0.8–2.5 (m, 6H), 5.45, 5.89 (AB, J ס 16.8 Hz, 5Ј-H2).
ם
ם
(30ЊC); m/z (%) 230 (6) [M ], 215 (32) [M מ CH3],
ם
183 (87) [M מ SCH3], 182 (100) [183 מ H,
ם
ם
ם
C11H18S ], 168 (33) [C10H16S , 5 ], 167 (73) [182 מ
Acid Cleavage of 11. Enol ether 11 (0.50 mmol)
was briefly refluxed with 2,4-DNPH in aqueous
ethanolic H2SO4. The orange crystals of (ע)-cam-
phor 2,4-dinitrophenylhydrazone (140 mg, 83%),
m.p. 156–158ЊC, were identified by mixed m.p. with
an authentic sample (164ЊC) [30].
ם
ם
CH3], 139 (49), 135 (51) [5 מ HS, C10H15], 127 (60),
119 (42), 93 (61) [C7H9 ], 91 (56) [C7H7 ], 81 (60)
[C6H9 ]. Anal. calcd for C12H22S2 (230.43): C, 62.54;
ם
ם
ם
H, 9.62; S, 27.83; found: C, 62.99; H, 9.46; S, 27.87.
The reaction with 2,4-DNPH in ethanolic H2SO4 (5
minutes on steam bath) gave rise to (מ)-fenchone
2,4-dinitrophenylhydrazone (87%) as orange nee-
dles, m.p. 159–162ЊC (mixed m.p.).
Thiofenchone S-Methylide (7) and Acids
Methanol. Compound 6 (210 mg, 1.00 mmol,
freshly recryst.) was heated in 10 mL of methanol in
a 45ЊC bath for 8 hours. After removal of methanol
at the rotary evaporator, the 1H NMR analysis
(CDCl3), based on the integrals of s at d 3.41 (OCH3)
and that of as-tetrachloroethane (d 4.28), indicated
96% of 20. PLC (petroleum ether/CH2Cl2 9:1) and
crystallization from methanol at מ78ЊC gave exo-2-
1-(Methylthio)-␣-fenchene (25).
Colorless oil
which solidifies at room temperature. 1H NMR
(CDCl3) d 0.78, 1.05 (2s, 2 CH3), 1.07–2.0 (m, 6 H),
2.07 (s, SCH3), 2.28–2.70 (m, 1 H), 4.83, 5.12 (2t, J Ϸ
2 Hz, H2Cס). Anal. calcd for C11H18S (182.32): C,
72.46; H, 9.95; S, 17.59; found: C, 72.42; H, 9.81; S,
17.54.

Thiofenchone S-Methylide and Its Spiro-1,3,4-thiadiazoline Precursor 143
Conversion of 25 to 2,7,7-Trimethylbicyclo[2.2.1]-
heptane (23,24). Compound 25 (550 mg, 3.02
2-Methylpropane-2-thiol. Thiadiazoline 6 (2.00
mmol) and 2.20 mmol of the thiol in 4 mL of abso-
lute THF were heated to 40ЊC for 8 hours (49 mL of
mmol) in 50 mL of absolute ethanol and ca. 15 g
Raney nickel (freshly prepared W2 [31]) were re-
fluxed for 20 hours, hot filtered, and washed with 3
ן 20 mL of hot ethanol. After adding H2O and 40
mL of pentane, the phase separation required 2 days.
The pentane was slowly distilled (Vigreux column)
from a 40ЊC bath; then distillation at 165ЊC (bath)
gave 245 mg of isobornylane as a 68:32 mixture of
endo-2-methyl (23) and exo-2-methyl (24) form. The
13C NMR spectrum showed 19 signals (20 expected;
coincidence: d at 45.0); 23 and 24 were identified
with the hydrogenation product of ␣-fenchene (see
1
N2). After removal of the solvent, the H NMR inte-
gral of the s at d 4.83 (vinyl-H), compared with that
of weighed trichloroethylene, indicated 59% of 1-
(methylthio)-␣-fenchene (25).
Cycloadditions of Thiofenchone S-Methylide (7)
Tetracyanoethylene (TCNE). Compound 6 (1.00
g, 5.94 mmol) and TCNE (900 mg, 7.03 mmol) in 5
mL of THF were reacted at 50ЊC for 2.5 hours (146
mL of N2, 98%). After evaporation, the minor cy-
cloadduct 28B (155 mg, 8%) crystallized from ether/
pentane (1:5), m.p. 163–165ЊC (dec.). The excess of
TCNE was removed by aqueous sodium sulfite, and
the residue of the mother liquor was subjected to
PLC (CH2Cl2). The main zone furnished the major
isomer 28A (445 mg, 24%), m.p. 163–164ЊC, from
methanol. In separate experiments in absolute THF
ם
below). MS (20ЊC); m/z (%) 138 (1.8) [M ], 123 (1.2)
ם
123 מ
C H
12], 83 (6), 69 (28)
[M מ CH3], 109 (3) [123 מ CH2], 95 (7) [
ם
ם
2 CH2, C7H
C H
5
11], 85 (6), 84 (93) [
6
ם
ם
C H
8 ].
[
9 ], 56 (100) [
4
Hydrogenationof(1S,4R)-(ם)-␣-Fenchene(26).
(ם)-␣-Fenchol was converted to the tosylate, m.p.
96–98ЊC, and the elimination of TsOH followed the
procedure (KF in diglycol) given by Hanack [32].
Spinning-band column distillation afforded 26, b.p.
155.8–156.4ЊC (156–157ЊC [32]). 13C NMR (CDCl3, 20
MHz) d 20.7, 21.7 (2q, 2 CH3), 28.6, 28.8 (2t, C-5, C-
6), 37.5 (t, C-3), 45.0 (d, C-4), 46.0 (s, C-7), 53.8 (d,
C-1), 103.0 (t, H2Cס), 156.3 (s, C-2). The hydrogen-
ation of 26 with Raney nickel and boiling ethanol
was carried out as described previously. The 13C
NMR spectrum of the product showed the same sig-
nals as the sample which originated from 25, but in
the ratio 23/24 ס 61:39. The comparison of H-de-
coupled and off-resonance spectrum provided the
multiplicities. The expectation that within each
group (3 CH3, 3 CH2, 3 CH, 1 Cq) integrals would be
similar for 23 on one side and for 24 on the other,
was fulfilled. The integrals clearly fell into two
groups of 9 ם 9 ם coincidence signal; isomer ratios
1
(or benzene), the crude product was H NMR-ana-
lyzed (CDCl3) vs. trichloroethylene as standard: the
s of CH3 at d 1.34 and 1.30 indicated 59% (62%) of
28A and 29% (27%) of 28B, corresponding to adduct
yields of 88% (89%).
3Ј,3Ј,4Ј,4Ј-Tetracyanospiro-[fenchane-2,2Ј-thio-
lane] (28). Isomer A. Colorless needles, m.p. 166–
167ЊC (dec.) from methanol at מ25ЊC. 1H NMR
(CDCl3) d 1.34, 1.64, 1.75 (3s, 3 CH3), 1.3–2.4 (m, 7
H), 3.65, 3.75 (AB, J ס 12.9 Hz, 5Ј-H2). 13C NMR
(CDCl3) d 21.2, 24.8, 31.1 (3q, 3 CH3); 25.3, 30.8, 39.0,
47.0 (4t, 4 CH2); 49.3 (d, C-4); 50.4, 53.9, 55.6, 57.1
(4s, C-1, C-3, C-3Ј, C-4Ј); 78.5 (s, C-2), 111.1, 111.55,
111.60, 111.9 (4s, 4 CN). MS (90ЊC); m/z (%): 310 (7)
ם
[M ], 257 (3), 232 (6), 228 (5), 199 (5), 168 (7)
ם
ם
ם
ם
[C10H16S , 5 ], 123 (13) [C9H15], 93 (6) [C7H9 ], 91 (6)
1
resulted from a statistical analysis. Note that H
ם
ם
[C7H7 ], 81 (100) [C6H9 ]. Anal. calcd for C17H18N4S
(310.41): C, 65.77; H, 5.85; N, 18.05; S, 10.33; found:
C, 65.61; H, 5.80; N, 18.15; S, 10.41.
NMR spectra (100 MHz) were useless for the anal-
ysis here.
In a further experiment, ␣-fenchene (26, 1.36 g,
10 mmol) in ethanol was shaken under H2 with Pd
(10% on carbon). After uptake of 206 mL of H2,
workup as above furnished 995 mg (72%) with a ra-
tio 23/24 ס 29:71. The isomer separation by chro-
Isomer B. Colorless needles from methanol,
m.p. 165–166ЊC (dec., mixed m.p. with A depressed).
1H NMR (CDCl3) d 1.30, 1.65, 1.83 (3s, 3 CH3), 1.5–
2.5 (m, 7 H), 3.75 (A2, 5Ј-H2); (C6D6): d 0.94, 1.21, 1.43
(3s, 3 CH3), 0.45–2.20 (m, 7 H), 2.44, 2.46 (AB, J ס
13.6 Hz, 5Ј-H2). 13C NMR (CDCl3) d 24.1, 24.6, 27.5
(3q, 3 CH3); 22.9, 38.9, 41.5, 44.2 (4t, 4 CH2); 51.1 (d,
C-4); 49.7, 50.7, 55.2, 55.7 (4s, C-1, C-3, C-3Ј, C-4Ј);
81.8 (s, C-2); 2 ן 111.4, 112.8, 113.0 (4s, 4 CN). Anal.
calcd for C17H18N4S (310.41): C, 65.77; H, 5.85; N,
18.05; S, 10.33; found: C, 65.60; H, 5.77; N, 17.78; S,
10.31.
1
matography did not succeed. H NMR (CDCl3, 80
MHz) of CH3 signals: d 0.94, 1.00, 1.03 for 23 and
0.94, 1.07, 1.08 for 24. 13C NMR CDCl3, 20 MHz) of
23: d 17.8, 20.96, 21.9 (3q, 3 CH3); 21.05, 29.8, 38.71
(3t, 3 CH2); 31.9, 45.0, 49.1 (3d, 3 CH); 47.9 (s, C-7);
24: 22.3, 22.93, 23.05 (3q, 3 CH3); 28.0, 31.4, 39.4 (3t,
3 CH2); 38.86, 45.0, 50.2 (3d, 3 CH); 46.3 (s, C-7).
Anal. calcd for C10H18 (138.24): C, 86.88; H, 13.12;
found: C, 86.58; H, 13.00.

144 Huisgen, Mloston, and Pro¨bstl
Maleic Anhydride. Compound 6 (2.97 mmol)
and maleic anhydride (freshly sublimated, 350 mg,
3.57 mmol) in 6 mL of THF were stirred in a 45ЊC
bath for 2.5 hours (73 mL of N2, 98%). Colorless crys-
tals of 29 (186 mg, 22%), m.p. 182–184ЊC, were ob-
tained from ether/pentane (1:1) and recrystallized
from CHCl3/ether. Bulb-to-bulb distillation of the
mother liquor at 60–65ЊC/1 mm gave 25 (203 mg,
38%) as a colorless liquid which glass-like solidified.
The product of a second experiment was subjected
C14H21N3O2S (295.40): C, 56.92; H, 7.17; N, 14.23; S,
10.86; found: C, 57.09; H, 7.30; N, 13.98; S, 10.83.
Isomer 30B. 1H NMR (CDCl3) d 1.11, 1.33, 1.36
(3s, 3 CH3); 1.40–2.20 (m, 7 H), 3.05 (s, NCH3), 4.48,
4.84 (AB, J ס 9.2 Hz, 5Ј-H2); (C6D6): d 0.98, 1.12, 1.38
(3s, 3 CH3), 0.65–2.00 (m, 7 H), 2.56 (s, NCH3), 3.99,
4.55 (AB, J ס 10.4 Hz). 13C NMR (20.2 MHz, C6D6) d
20.7, 24.1, 26.0, 29.0 (4q, 4 CH3); 25.3, 32.2, 46.0, 50.0
(4t, 4 CH2); 49.3, 52.4 (2s, C-1, C-3), 94.4 (S, C-2);
151.1, 155.9 (2s, 2 CסO); the 13C signal intensities
point to A/B ס 60:40.
1
to H NMR analysis with sym-tetraychloroethane:
the broad s of vinyl-H at d 4.83 indicated 27% of 25,
and the m at 3.6–4.0 showed 43% of 29.
Thiobenzophenone.
From 6 (511 mg, 2.43
Spiro[fenchane-2,2Ј-thiolane]-3Ј,4Ј-dicarboxylic
anhydride (29). m.p. 185–186ЊC. H NMR (CDCl3)
mmol) and 31 (963 mg, 4.86 mmol, freshly distilled)
in 8 mL of THF at 50ЊC, 98% of N2 was eliminated
in 2.5 hours. Trituration of the crude product with
ether left undissolved 853 mg (86%) of 4,4,5,5-tetra-
phenyl-1,3-dithiolane (33), m.p. 205–208ЊC; after re-
crystallization from CHCl3/pentane, the colorless 33
showed m.p. 206–208ЊC (dec., blue; 199–200ЊC [33],
1
d 1.08, 1.20, 1.35 (3s, 3 CH3), 1.5–2.5 (m, 7H), 2.95–
3.50 (m, 2H), 3.58–4.00 (m, 2H). MS (80ЊC); m/z (%):
ם
ם
280 (21) [M ], 237 (12), 207 (9), 197 (35) [M -C6H11],
ם
ם
ם
125 (41) [C9H17], 123 (73) [C9H15], 83 (22) [C6H11], 81
ם
(100) [C6H9 ]. Anal. calcd for C15H20O3S (280.38): C,
1
64.25; H, 7.19; S, 11.44; found: C, 64.44; H, 7.17; S,
11.42.
205–207ЊC [15]), and was identified by its H NMR
spectrum [15]. Anal. calcd for C27H22S2 (410.58): C,
78.98; H, 5.40; S, 15.62; found: C, 78.83; H, 5.40; S
15.60.
4-Methyl-1,2,4-triazoline-3,5-dione. Compound
6 (7.36 mmol) and 1.00 g (8.83 mmol) of the cyclic
azo compound in 12 mL of THF were reacted at 50ЊC
for 3 hours (100% N2). After removal of the solvent,
the residue in CH2Cl2 was extracted with 10% aque-
ous Na2SO3. The residue of the organic phase was
separated by PLC (CH2Cl2): fenchone (347 mg, 30%),
30B (90 mg, 4%) as a pale-yellow oil, and 30A (224
mg, 10%), was eluted with ethyl acetate and crystal-
lized from benzene/methanol, m.p. 162–165ЊC (dec.,
Thioxanthione (37). Compounds 6 (420 mg,
2.00 mmol) and 37 (502 mg, 2.20 mmol) in 6 mL of
THF at 40ЊC were stirred for 8 hours (49 mL of N2,
98%). Evaporation of THF and trituration with
CDCl3 at 0ЊC left 41 (280 mg, 30%) undissolved, m.p.
170–172ЊC (168–170ЊC [24]). After addition of a
weighed amount of sym-tetrachloroethane, the AB
systems of 5Ј-H2 at d 3.3–4.0 indicated 49% of 36A
and 36B. In the separation by PLC (petroleum ether/
CH2Cl2 7:3), thiofenchone (5) moved as the first frac-
tion and was identified by its RF. The second fraction
(280 mg, 34%), colorless crystals, m.p. 168–175ЊC,
showed after recrystallization from CH2Cl2/ethanol
still the broad m.p. 173–178ЊC, and consisted of 36,
A/B ס 85:15 (13C NMR integrals). Our attempts of
separating the exo, endo isomers by chromatography
or fractional crystallization failed.
1
red). In a second experiment, the H NMR analysis
(C6D6) was based on the AB spectra for 5Ј-H2 of 30A
and 30B and the s of trichloroethylene as weight
standard, and indicated 54% of 30; the s of NCH3
(C6D6) showed A/B ס 55:45.
Spiro[fenchane-2,2Ј-(1,3,4)-triazolidine]-3Ј,4Ј-di-
carbox(N-methylimide) (30). Isomer 30A. 1H NMR
(CDCl3) d 1.02, 1.28, 1.30 (3s, 3 CH3), superimposed
by 0.9–3.05 (several m, 7 H), 3.06 (s, NCH3), 4.47,
4.60 (AB, J ס 9.5 Hz, 5Ј-H2); (C6D6): d 0.89, 1.02, 1.40
(3s, 3 CH3), 0.8–1.7 (m, 7 H), 2.69 (s, NCH3), 3.12
(dq, J ס 10.0, ϳ2 Hz, 1 H), 3.93, 4.04 (AB, J ס 10.0
Hz, 5Ј-H2). 13C NMR (20.2 MHz, C6D6); d 17.5, 2 ן
25.2, 26.6 (3q, 4 CH3); 24.5, 37.6, 43.2 (3t, 3 CH2),
41.1 (dd, probably C-5Ј), 49.6 (d, C-4), 51.3, 51.6 (2s,
C-1, C-3), 91.7 (s, C-2), 146.2, 149.9 (2s, 2 CסO). MS
Dispiro[1,3-dithiolane-4,9Ј;5,9Љ-bis(thioxan-
thene)] (41). 1H NMR (C6D6): d 3.84 (s, 2-H2), 6.20,
6.83, 7.16, 7.75 (4m, 16 arom. H); (CDCl3): d 4.48 (s,
2-H2). Anal. calcd for C27H18S4 (470.68): C, 68.90; H,
3.85; S, 27.25; found: C, 69.25; H, 3.95; S, 27.24.
Dispiro[fenchane-2,5Ј-(1,3)-dithiolane-4Ј,9Љ-thi-
oxanthene] (36). Adduct 36A. 1H NMR (CDCl3) d
1.12 (s, 2 CH3), 1.25 (s, CH3), 1.3–2.0 (m, 7 H), 3.53
and 3.84 (AB, J ס 12.0 Hz, 5Ј-H2), 7.0–7.5, 7.8–8.1
(2m, 6 ם 2 arom. H). 13C NMR (CDCl3, 20 MHz) d
ם
(80ЊC), m/z (%): 295 (30) [M ], 240 (3), 212 (10), 210
ם
ם
(16), 182 (15), 168 (100) [C10H16S , 5 ], 153 (13), 135
ם
(41) [168 - SH, C10H15], 125 (23), 113 (21), 112 (18),
ם
ם
91 (15) [C7H7 ], 81 (66) [C6H9 ]. Anal. calcd for

Thiofenchone S-Methylide and Its Spiro-1,3,4-thiadiazoline Precursor 145
[3] Krapcho, A. P.; Silvon, M. P.; Goldberg, I.; Jahngen,
E. G. E., Jr., J Org Chem 1974, 39, 860.
[4] Huisgen, R.; Mloston, G. Polish J Chem 1999, 73, 635.
[5] Sustmann, R.; Sicking, W.; Huisgen, R. J Org Chem
1993, 58, 82.
20.6, 26.6, 33.0 (3q, 3 CH3), 26.0, 34.1, 43.4, 43.5 (4t,
4 CH2), 49.6 (d, C-4), 126.0, 126.1, 126.5, 126.8, 127.5
(5d, 8 arom. CH), 48.5, 56.2, 71.1, 87.2 (4s, 4 aliph.
Cq), 134.2, 134.3, 138.5, 139.0 (4s, 4 arom. Cq). MS
ם
ם
(90ЊC); m/z (%) 410 (0.1) [M ], 242 (2.2) [C14H10S2 ,
[6] Review: Fisera, L.; Huisgen, R.; Kalwinsch, I.; Lang-
M
ם מ 5; 13C2 ם 34S calcd/found 0.22/0.19], 228 (0.5)
ם ם ם
hals, E.; Li, X.; Mloston, G.; Polborn, K.; Rapp, J.;
Sicking, W.; Sustmann, R. Pure Appl Chem 1996, 68,
789.
[C13H8S2 , 37 ], 210 (100) [C14H10S , 9-Methylene-
thioxanthene ; 13C 16/15; 13C2 ם 34S 0.22/0.19], 178
ם
[7] (a) Huisgen, R.; Mloston, G.; Langhals, E. J Org Chem
1986, 51, 4085; See also (b) Huisgen, R. Chem Pharm
Bull 2000, 48, 757.
[8] Preliminary communication: Huisgen, R.; Mloston,
G.; Pro¨bstl, A. Tetrahedron Lett 1985, 26, 4431.
[9] Beiner, J. M.; Lecadet, D.; Paquer, D.; Thuillier, A.;
Vialle, J. Bull Soc Chim Fr 1973, 1979.
[10] Beckmann, S.; Mezger, R. Chem Ber 1956, 89, 2738.
[11] Brown, H. C.; Deck, H. R. J Am Chem Soc 1965, 87,
5620.
[12] Dagonneau, M.; Paquer, D.; Vialle, J. Bull Soc Chim
Fr 1973, 1699.
[13] Lottes, A. C.; Landgrebe, J. A.; Larsen, K. Tetrahedron
Lett 1989, 30, 4089.
[14] 1,4-H Shift in thiocarbonyl ylides: Huisgen, R.; Mlos-
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Acta 1995, 78, 1067.
(4.2) [C14H10, 210 מ S, 13C 0.66/0.65; 13C2 0.05/0.05,
ם
ם
ם
ם
S-free], 168 (0.7) [C10H16S , 5 ], 165 (8) [C10H13, flu-
orenyl ], 152 (1.4) [C12H8 ], 135 (0.5) [168 מ SH],
123 (1.7) [C9H15], 91 (1) [C7H7 ], 81 (4) [C6H7 ].
ם
ם
ם
ם
ם
Adduct 36B. 13C NMR (CDCl3) d 19.0, 29.1, 29.9
(3q, 3 CH3), 26.0, 33.2, 42.4, 44.8 (4t, 4 CH2), 49.8 (d,
C-4), 47.2, 57.4, 70.9, 85.9 (4s, 4 aliph. Cq), 125.5,
127.0, 127.1, 127.3 (4d, 8 arom. CH), 128.8 (s, only
1 arom. Cq visible). Anal. calcd for C24H26S3 (410.65,
85:15 mixture): C, 70.19; H, 6.38; S, 23.43; found: C,
69.92; H, 6.18; S, 23.39.
Hydrogenolysis of 36. 615 mg (1.50 mmol) and
ϳ 5 g Raney nickel [31] in 20 mL of ethanol were
refluxed for 10 hours, filtered, washed with hot eth-
anol, diluted with 50 mL of H2O, and extracted with
3 ן 30 mL of pentane. After distillation of pentane
over a column, fenchane (125 mg, 60%) distilled at
[15] Huisgen, R.; Kalwinsch, I.; Li, X.; Mloston, G. Eur J
Org Chem 2000, 1685.
[16] Mloston, G.; Huisgen, R. Tetrahedron, in press.
[17] Rearrangements in fenchyl series: Hu¨ckel, W.; Volk-
mann, D. Liebigs Ann Chem 1963, 664, 31.
[18] Nametkin, S. Liebigs Ann Chem 1924, 440, 60; Toi-
vonen, N. J.; Alfthan, V.; Bo¨o¨k, L. H.; Erich, M. I.;
Heino, E. K. J Prakt Chem 1941, 159, 70.
[19] Brown, H. C.; Kawakami, J. H. J Am Chem Soc 1970,
92, 1990.
1
60–80ЊC (bath)/10 mm as a colorless oil; H NMR
(CDCl3) d 0.95 (s, 2 CH3), 1.05 (s, CH3), 1.05–1.8 (m,
9H). The residue in the microflask consisted of 1,1-
diphenylethane (215 mg), 1H NMR-identified with an
authentic sample; 1H NMR (CDCl3) d 1.52 (d, J ס 7.2
Hz, CH3), 3.99 (q, J ס 7.2 Hz, 1-H), 7.06 (s, 2 C6H5).
[20] Rousseau, C.; Errard, M.; Petit, F. J Mol Catal 1979,
5, 163.
[21] Schumann, D.; Frese, E.; Scho¨nberg, A. Ber Dtsch
Chem Ges 1969, 102, 3192. Paquer, D.; Morin, L.; Va-
zeux, M.; Andrieu, C. G. Rec Trav Chim Pays-Bas
1981, 100, 36, 52.
ACKNOWLEDGMENTS
[22] Huisgen, R.; Li, X.; Mloston, G.; Fulka, C. Eur J Org
Chem 2000, 1695.
[23] Giera, H. Ph.D. Thesis, University of Munich, Mu-
nich, Germany, 1991.
[24] Scho¨nberg, A.; Kaltschmitt, H.; Schulten, H. Ber
Dtsch Chem Ges 1933, 66, 245.
[25] Mloston, G.; Huisgen, R.; Polborn, K. Tetrahedron
1999, 55, 11475.
We express sincere thanks to the Fonds der
Chemischen Industrie, Frankfurt, for kind support of
our research work. G. M. thanks the Alexander von
Humboldt Foundation for a stipend. We are grateful
to Helmut Huber for help with the NMR spectra, to
Reinhard Seidl for the mass spectra, and to Helmut
Schulz and Magdalena Schwarz for the elemental
analyses.
[26] Mloston, G.; Huisgen, R.; Huber, H.; Stephenson, D.
S. J Heterocyclic Chem 1999, 36, 959.
[27] Huisgen, R.; Mloston, G.; Polborn, K. Heteroatom
Chem 1999, 10, 662.
[28] Sen, D. C. J Ind Chem Soc 1935, 12, 647.
[29] Barton, D. H. R.; Guziec, F. S.; Shahak, I. J Chem Soc
Perkin Transl 1 1974, 1794.
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