Studies on the flash vacuum thermolysis of thiones of selected N-, O-, and S-heterocycles

Article abstract of DOI:10.1002/hlca.200690104

Thermal decomposition of thiones of selected N-, O- and S-heterocycles under flash vacuum thermolysis conditions was investigated. In the case of six-membered 4H-3,1-benzoxathiin-4-thione 6, the course of the reaction depended on the substitution pattern at C(2) (Scheme 3). Thus, the 2-unsubstituted derivative 6a led to the unstable product 2, which upon treatment with MeOH was converted quantitatively into methyl 2-mercaptobenzoate (7). The analogous thermolysis of the 2,2-dimethyl derivative 6b yielded 2-methyl-4H-1- benzothiopyran-4-thione (8) as a sole product. In the case of thiophthalide derivatives 15, a thermal rearrangement in the gas phase leading to the corresponding benzo[c]thiophen-1(3H)-ones 16 in high yields was observed (Scheme 6). Unexpectedly, thionation of 1,3-oxathiolan-5-one 17 with Lawesson's reagent under standard conditions led to 1,2-dithietane derivative 19, which, after the gas-phase thermolysis, underwent a ring enlargement to yield 3H-1,2-dithiole 20 (Scheme 7). The six-membered 4H-1,3-benzothiazine-4-thione 21 was shown to give three products: phenanthro[9,10-c]-1,2-dithiete (22), 3H-1,3-benzodithiole-3- thione (23), and N-(3H-1,2-benzodithiol-3-ylidene)prop-2-en-1-amine (24) (Scheme 8). The latter is the product of the initial reaction, whereas 22 and 23 are postulated to be formed as secondary products of the conversion of the intermediate 6-(thioxomethylene)cyclohexa-2,4-diene-1-thione (26) (Schemes 9 and 10).

Full text of DOI:10.1002/hlca.200690104

Helvetica Chimica Acta – Vol. 89 (2006)
991
Studies on the Flash Vacuum Thermolysis of Thiones of Selected N-, O-, and
S-Heterocycles
1
by Tomasz Drewnowski ), Stanisław Le s´ niak*, and Grzegorz Mlosto n´
Department of Organic and Applied Chemistry, University of Łód z´ , 68 Narutowicza, PL-90 136 Łód z´
(
phone: +48426355765, fax:+48426781609; e-mail: slesniak@chemul.uni.lodz.pl)
and Renata Siedlecka, and Jacek Skar z˙ ewski
Section of Organic Chemistry, Wrocław University of Technology, PL-50 370 Wrocław
Thermal decomposition of thiones of selected N-, O- and S-heterocycles under flash vacuum ther-
molysis conditions was investigated. In the case of six-membered 4H-3,1-benzoxathiin-4-thione 6, the
course of the reaction depended on the substitution pattern at C(2) (Scheme 3). Thus, the 2-unsubstituted
derivative 6a led to the unstable product 2, which upon treatment with MeOH was converted quantita-
tively into methyl 2-mercaptobenzoate (7). The analogous thermolysis of the 2,2-dimethyl derivative 6b
yielded 2-methyl-4H-1-benzothiopyran-4-thione (8) as a sole product. In the case of thiophthalide deriv-
atives 15, a thermal rearrangement in the gas phase leading to the corresponding benzo[c]thiophen-
1
(3H)-ones 16 in high yields was observed (Scheme 6). Unexpectedly, thionation of 1,3-oxathiolan-5-
one 17 with Lawessonꢀs reagent under standard conditions led to 1,2-dithietane derivative 19, which,
after the gas-phase thermolysis, underwent a ring enlargement to yield 3H-1,2-dithiole 20 (Scheme 7).
The six-membered 4H-1,3-benzothiazine-4-thione 21 was shown to give three products: phenan-
thro[9,10-c]-1,2-dithiete (22), 3H-1,3-benzodithiole-3-thione (23), and N-(3H-1,2-benzodithiol-3-ylide-
ne)prop-2-en-1-amine (24) (Scheme 8). The latter is the product of the initial reaction, whereas 22 and
2
3 are postulated to be formed as secondary products of the conversion of the intermediate 6-(thioxome-
thylene)cyclohexa-2,4-diene-1-thione (26) (Schemes 9 and 10).
1
. Introduction. – It is well documented that the flash vacuum thermolysis of 2-mer-
captobenzoic acid (1) leads to the formation of benzothiet-2-one (2) (Scheme 1) [1].
The same product can be obtained thermally from benzothiophene-2,3-dione [1] as
well as photolytically starting either from 4H-1,2,3-benzothiadiazin-4-one [2] or from
2-phenyl-4H-3,1-benzoxathin-4-one [3]. The benzothiet-2-one (2) is postulated to
exist in an equilibrium with a-thioxo ketene 3 being its ring-opened isomer. The hetero-
cycle 2 is stable only below ꢀ208, whereas the analogous naphtho[2,3-b]thiet-2-one was
successfully isolated and identified at room temperature [4]. It is worth mentioning that
the treatment of 2-mercaptobenzoic acid with molecular sieves at room temperature in
the presence of suitable dienophiles, e.g., dimethyl fumarate, yields hetero-Diels–Alder
cycloadducts in excellent yields [5]. This result shows that the elimination of H O lead-
2
ing to highly reactive heterocumulene occurs even under very mild conditions.
1)
Part of the planned Ph. D. Thesis by T. Drewnowski, University of Łód z´ .
ꢁ
2006 Verlag Helvetica Chimica Acta AG, Zürich

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Helvetica Chimica Acta – Vol. 89 (2006)
Scheme 1
The generation of heterocumulenes of type 5 is based on the thermolysis of 4H-1,3-
dioxin-4-ones 4, which are known to eliminate a molecule of ketone (Scheme 2). As
already reported, the replacement of the C=O group by a C=S unit in the case of
the substrates 4 does not influence the main course of the reaction [6–8].
Scheme 2
The present paper is aimed mainly at the study on the influence of the C=S group
on the course of the gas-phase thermolysis of selected cyclic derivatives of 2-mercapto-
benzoic acid. For comparison, some five-membered systems bearing a thioxo group as
well as a cyclic six-membered thioamide are included for mechanistic investigations.
2
. Results and Discussion. – The 4H-3,1-benzoxathiin-4-thione (6a) obtained after
thionation of the corresponding oxo analogue [9] was used as the first compound in the
ꢀ3
2
study. Thermolysis carried out at 8508/1.5 · 10 Torr ) led to the formation of an orange
pyrolyzate which, after warming to room temperature, immediately decomposed giving
a colorless, viscous material. However, treatment of the colored product collected on
the cooling finger at ꢀ788 with MeOH resulted in the formation of a compound,
which could be easily isolated and identified as methyl 2-mercaptobenzoate (7)
(Scheme 3). This result showed unambiguously that the initially formed product in
the thermolysis of 6a was benzothiet-4-one (2). The analogous experiment with 2,2-
dimethyl-4H-3,1-benzoxathiin-4-thione (6b) gave a yellow solid, which did not change
during the warming to room temperature. The spectroscopic data allowed to identify
this product as the known 2-methyl-4H-1-benzothiopyran-4-thione (8) (Scheme 3) [10].
The comparison of the results obtained with 6a and 6b shows that the substituent R
attached at C(2) governs the course of the reaction in the gas phase and thereby deter-
mines the type of the formed products. Whereas in the case of 6a, elimination of thio-
formaldehyde took place, the reaction with 6b proceeded by elimination of H O. In the
2
light of available literature reports [6–8], the elimination of formaldehyde rather than
2)
The temperature 8508 is the lowest possible at which the starting material was not present in the
pyrolyzate.

Helvetica Chimica Acta – Vol. 89 (2006)
993
Scheme 3
thioformaldehyde could be expected in the case of 6a. The preservation of the carbonyl
group in the product can be rationalized by the assumption that the initial step of the
reaction is the rearrangement of the O-substituted thiolactones into the S-substituted
isomer, which finally eliminates of H C=S (Scheme 4). This type of isomerization is
2
known as the Schçnberg–Newman–Kwart rearrangement, and to the best of our knowl-
edge, hitherto it has been reported only for reactions carried out in solution but not in
the gas phase [11].
Scheme 4
It is very likely that this type of rearrangement initiates also the conversions of 6b in
the gas phase (Scheme 5). Selective splitting of the CꢀS bond in the rearranged product
10 affords the biradical intermediate 11, in which subsequent migration of an H-atom
leads to the unstable thioacid 12. The postulated abstraction of the H-atom by the O-
and not the S-atom can be rationalized by the assumption that an O-atom displays
higher affinity to an H-atom than an S-atom [12]. The next step of the conversion of
1
2 to 8 requires elimination of H O which presumably proceeds stepwise via homolytic
2
cleavage of the CꢀOH bond leading to 13, which undergoes cyclization to 14. The latter
eliminates the H-atom giving the final product 8 (Scheme 5).
The next compounds involved in the study were thiophthalides 15a,b. Flash vacuum
ꢀ
3
thermolysis of 15a at 8508/1.5 · 10 Torr occurred smoothly, and the expected product
of the gas-phase rearrangement, i.e., benzo[c]thiophen-1(3H)-one (16a), was obtained
in nearly quantitative yield. Similarly, the 3,3-dimethyl derivative 15b was converted
into the analogous thiophenone 16b (Scheme 6). These results establish that the rear-
rangement of thio-O-lactones to thio-S-lactones by exchange of the positions of both
3
heteroatoms proceeds easily also in the gas phase ). It is worth mentioning that in
3)
Heating of 15a in boiling aniline was reported to yield 16a [13], and 15b was converted to 16b by the
reaction with triethyloxonium tetrafluoroborate and triethylamine [14].

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Helvetica Chimica Acta – Vol. 89 (2006)
Scheme 5
the case of 15b the conversion analogous to 6b ! 8, which requires elimination of H O
2
(Scheme 5), was not observed.
Scheme 6
Cammeron and Pinnick reported that 1,3-oxathiolan-5-ones of type 17 eliminate
CO in the gas phase to generate the reactive ꢂthiocarbonylꢀ ylides (=sulfonium ylides),
2
which underwent stereoselectively 1,3-dipolar electrocyclization to give the corre-
sponding thiiranes [15]. In the light of the results described for 6, it was of interest to
examine whether the thioxo derivative 18 follows a reaction pathway similar to that
presented for 6b. However, the attempted thionation of 17 with Lawessonꢀs reagent
1
13
(
LR) in boiling xylene led to 1,2-dithietane 19, as a single isomer ( H- and C-
NMR) with unknown configuration, and the expected product 18 was not observed
Scheme 7). Having in hands this new, S-rich heterocycle 19, we decided to examine
its behavior in the gas-phase thermolysis. Under the conditions outlined in Scheme 7,
(

Helvetica Chimica Acta – Vol. 89 (2006)
995
Scheme 7
3
-benzylidene-4-methyl-3H-dithiolane (20) was obtained as a 1:3-(E)/(Z) mixture
13
4
(based on the C-NMR spectrum) ). Unfortunately, all attempts to separate the iso-
mers by column chromatography or prep. TLC were in vain.
The 4H-1,3-benzothiazine-4-thione 21, which is an N-analogue of 6b, was obtained
from the corresponding oxo derivative by treatment with LR in boiling xylene. Due to
the replacement of an O- by an N-atom, this compound did not undergo the Schçn-
berg–Newman–Kwart rearrangement. The gas-phase thermolysis led to a mixture of
three products, which were separated by column chromatography. Based on the spec-
troscopic and physicochemical properties, their structures were elucidated as 22–24
(Scheme 8). This result suggests that the key intermediate in the reaction is the biradical
25, which either eliminates propan-2-imine to give heterocumulene 26 or undergoes an
intramolecular cyclization followed by the elimination of an H-atom leading finally to
the isolated amine 24 (Scheme 9). It is very likely that the formation of 22 and 23 pro-
ceeds by initial dimerization of 26 and subsequent unsymmetrical fragmentation (the
symmetrical cleavage would lead to the starting 26) to give 3H-1,2-benzodithiole-3-thi-
one (23) and phenanthro[9,10-c]-1,2-dithiete (22) as a result of the dimerization of the
biradical or carbene (Scheme 10).
Scheme 8
On the other hand, the higher yield of 22 in comparison with 23 (theoretically, 1 mol
of 21 affords 0.5 mol of 23 and 0.25 mol 22) suggests that the additional amount of com-
4)
Interestingly, (E)- and (Z)-20 showed identical chemical shifts for all groups of signals in the H-
1
NMR spectrum (200 MHz).

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Helvetica Chimica Acta – Vol. 89 (2006)
Scheme 9
Scheme 10

Helvetica Chimica Acta – Vol. 89 (2006)
997
pound 22 originates from the decomposition of 23 initially formed in the gas phase. As a
matter of fact, when pure 23 was pyrolyzed under the same conditions, a mixture of 22
and 23 was obtained. This result shows unequivocally that 22 was produced from the
dimer of 26 as well as from 23.
In summary, the present study shows that the replacement of the O-atom in the
C=O group of the cyclic ester (lactone) by an S-atom results in the initial rearrange-
ment in the gas-phase thermolysis. The next step of the conversion depends strongly
on the substitution pattern at the C(2) atom of the heterocycle. Whereas in the case
of a CH group, the elimination of CH =S takes place to yield the reactive system
2
2
2
Ð 3, the presence of a Me
A
H
R
U
G
pyran-4-thione 8 via elimination of H O. Introduction of an N-atom into the six-mem-
2
bered heterocycle (thioamide instead of thioester) prevents the Schçnberg–Newman–
Kwart rearrangement and results in the competitive elimination of propan-2-imine
or dehydrogenation.
The authors thank the Polish State Committee for Scientific Research for financial support (Grant No.
3
T09A 046 25) and acknowledge the support by the Rector of the University of Łód z´ (Grant 505/740).
Experimental Part
1. General: Column chromatography (CC): silica gel (Merck60 , 63–200 microns). TLC: Merck-5554
aluminium-backed SiO plates; visualization by UV light. M.p.: Botius apparatus; uncorrected. IR Spec-
2
ꢀ
1
1
13
tra: Thermo-Nicolet-Nexus-FT-IR spectrometer; in KBr or as films, in cm . H- and C-NMR Spectra:
Varian-Gemini-200-BB-VT instrument, at 200.11 ( H) and 50.33 MHz ( C); CDCl solns. at ca. 218;
1
13
3
chemical shifts d in ppm rel. to SiMe , coupling constants J in Hz; assignments usually with ATP or
4
DEPT experiments. EI-MS: Finnigan-MAT-95 spectrometer at 70 eV; peaks ꢁ10% rel. intensity are
given in m/z (rel.%).
2. Starting Materials. Compounds 15a,b were prepared following the literature procedure, i.e., isoben-
zofuran-1(3H)-thione (15a) [16] and 3,3-dimethyl-isobenzofuran-1(3H)-thione (15b) [14]. The remaining
thiones 6a,b, and 21 as well as 19 were prepared by thionation of their ketone precursors with Lawesson
reagent (LR), i.e., of 4H-3,1-benzoxathiin-4-one [9], 2,2-dimethyl-4H-3,1-benzoxathiin-4-one [9], 2,2-
dimethyl-2,3-dihydro-4H-1,3-benzothiazin-4-one [17], and 2,2-dimethyl-4-phenyl-[1,3]oxathiolan-5-one
(17) [18].
3. Synthesis of 6a,b, 19 and 21: General Procedure. A soln. of the corresponding ketone (5 mmol) and
LR (3.24 g, 8 mmol) in xylene (20 ml) was heated to reflux for 4 h. Xylene was evaporated and the res-
idue was subjected to CC (SiO , hexane/CH Cl or hexane/AcOEt). Then, the products were purified
2
2
2
additionally by recrystallization.
4
H-3,1-Benzoxathiin-4-thione (6a). CC (hexane/CH Cl 1:1) and recrystallization from hexane gave
2 2
3
1
10 mg (34%) of 6a. Red solid. M.p. 64–668 (hexane). IR (KBr): 3052w, 2976s, 1583s, 1449s, 1427s,
296m, 1254s, 1224vs, 1135m, 1111m, 955w, 919s, 759vs, 713w, 642m. H-NMR: 5.40 (s, 2 H); 7.14–7.52
1
(
m, 3 H); 8.40–8.56 (m, 1 H). Anal. calc. for C H OS (182.26): C 52.72, H 3.32, S 35.19; found: C
8 6 2
5
2.48, H 3.51, S 35.11.
,2-Dimethyl-4H-3,1-benzoxathiin-4-thione (6b). CC (hexane/CH Cl 3 :2) and recrystallization from
2
2
2
hexane gave 631 mg (60%) of 6b. Red solid. M.p. 67–698 (hexane). IR (KBr): 3065w, 3046w, 2978m,
2
9
961m, 1581s, 1550m, 1446s, 1425s, 1366m, 1285w, 1259s, 1224vs, 1158m, 1132m, 1019vs, 1002s, 957w,
19s, 763vs, 696w. H-NMR: 1.73 (s, 6 H); 7.20–7.48 (m, 3 H); 8.35–8.52 (m, 1 H). Anal. calc. for
1
C H OS (210.32): C 57.11, H 4.79, S 30.49; found: C 57.08, H 4.55, S 30.21.
10
10
2
4
-Benzylidene-3,3-dimethyl-1,2-dithietane (19). CC (hexane/AcOEt 97:3) and recrystallization from
pentane gave 505 mg (45%) of 19. M.p. 51–528 (pentane). IR (KBr): 3077w, 3052w, 2958m, 2921m,
596w, 1577m, 1537s, 1489m, 1444s, 1382w, 1362s, 1170m, 1148s, 1107m, 1073w, 1030w, 920m, 823m,
1

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Helvetica Chimica Acta – Vol. 89 (2006)
1
13
7
40vs, 683s. H-NMR: 1.89 (br. s, 6 H); 6.31 (s, 1 H); 7.18–7.51 (m, 5 H). C-NMR (CDCl ): 31.8 (Me);
3
6
5.6 (C); 112.7 (CH); 126.7 (arom. C); 127.9 (arom. C); 128.8 (arom. C); 134.6 (C); 134.7 (C). MS: 208
+
(
27, M ), 194 (10), 193 (100), 134 (10). Anal. calc. for C H S (208.35): C 63.41, H 5.81, S 30.78; found: C
11
12 2
6
3.38, H 5.84, S 30.41.
,2-Dimethyl-2,3-dihydro-4H-1,3-benzothiazine-4-thione (21). CC (hexane/CH Cl 1:1) and recrys-
2
2
2
tallization from hexane/CH Cl gave 1005 mg (96%) of 21. Yellow solid. M.p. 191–1928 (hexane/
2
2
CH Cl ). IR (KBr): 3148m (NH), 3069m, 2984m, 2960w, 2937w, 1584w, 1567s, 1521vs, 1453m, 1425s,
2
2
1
1
387m, 1367m, 1225vs, 1160w, 1148w, 1000m, 768vs, 753w, 722m. H-NMR: 1.70 (s, 6 H); 7.10–7.45
(
m, 3 H); 8.48–8.65 (m, 1 H); 8.95 (br. s, 1 H). Anal. calc. for C H NS (209.33): C 57.38, H 5.30, N
10
11
2
6
.69, S 30.49; found: C 57.35, H 5.29, N 6.60, S 30.24.
. Thermolysis of Thiones: General Procedure. The flash vacuum thermolysis was carried out in a
4
2
ꢀ3
3
0·2.5 cm electrically heated horizontal quartz tube packed with quartz rings at 1.5 · 10 Torr. The start-
ing compounds (2 mmol) were slowly sublimed from a flask held at 40–508 (for 6a,b, 15a,b, and 19) or 808
for 21) into the thermolysis tube preheated to 8508. The products were collected in a CO /aceton trap.
(
2
After thermolysis, the system was brought to atmospheric pressure allowing a slow warming up to r.t., and
the products were dissolved in MeOH or CHCl . The solvent was evaporated and the products were puri-
3
fied by CC (SiO ), recrystallization, distillation, or prep. TLC.
2
Thermolysis of 6a. The product of the thermolysis was rinsed from the cold finger with cold MeOH.
After warming to r.t., excess MeOH was evaporated: 316 mg (94%) of methyl 2-mercaptobenzoate (7).
Thermolysis of 6b. The product of the thermolysis was rinsed from the cold finger with CHCl . Evap-
3
oration and recrystallization from hexane gave 342 mg (89%) of 2-methyl-4H-1-benzothiopyran-4-thione
(
8). M.p.107–1088 ([10]: 107–1088). Spectral data: identical with those of an authentic sample [10].
Thermolysis of 15a,b. The products of the thermolysis were rinsed from the cold finger with CHCl
Evaporation, CC (SiO , hexane/AcOEt 99 :1), and recrystallization from petroleum ether gave 291 mg
3
.
2
(
97%) of benzo[c]thiophen-1(3H)-one (16a) or 338 mg (95%) of 3,3-dimethyl-benzo[c]thiophen-1(3H)-
one (16b).
1
1
6a: M.p. 60–618 ([19]: 58–608). Spectral data: identical with those in [19].
6b: M.p. 47–488 ([20]: 46–488). Spectral data: identical with those in [14].
Thermolysis of 19. The products of the thermolysis were rinsed from the cold finger with CHCl .
3
ꢀ
2
Evaporation and CC (SiO , hexane/AcOEt 99 :1) followed by bulb-to-bulb distillation at 508/5 · 10
2
Torr gave 224 mg (54%) of 3-benzylidene-4-methyl-3H-1,2-dithiole (20). Colorless oil. IR (neat):
3
1
082w, 3060m, 2970w, 2947w, 2921m, 2863w, 1598m, 1497s, 1452m, 1430w, 1380w, 1333w, 1203m,
1
073m, 1032w, 922w, 916w, 855m, 838m, 759s, 690m. H-NMR: 2.28 (br. s, 3 H); 6.84 (br. s, 1 H); 7.12
13
(
br. s, 1 H); 7.17–7.40 (m, 3 H); 7.53–7.63 (m, 2 H). C-NMR: major isomer: 144.2, 138.7, 134.7 (3 C);
1
1
1
6
28.9, 127.4, 125.8, 125.6, 120.3 (5 CH); 16.0 (Me); minor isomer: 143.3, 137.2, 136.3 (3 C); 128.7,
28.4, 127.1, 123.1, 122.1 (5 CH); 15.7 (Me). MS (isomer mixture): 206 (11, M ), 205 (20), 204 (100),
+
90 (23), 174 (41), 173 (29), 128 (11), 115 (17), 1021 (13), 89 (13). Anal. calc. for C H S (206.32): C
11
10 2
4.03, H 4.89, S 31.08; found: C 64.00, H 4.81, S 30.88.
Thermolysis of 21. The products of the thermolysis were rinsed from the cold finger with CHCl3.
Evaporation and CC (silica gel, hexane/AcOEt) gave 84 mg (70%) of 22, after recrystallization from hex-
ane/CHCl , 77 mg (42%) of 23, after recrystallization from hexane/CH Cl , and 40 mg (9%) of 24, after
3
2
2
further purification by TLC (SiO , hexane/AcOEt 9 :1).
2
Phenanthro[9,10-c]-1,2-dithiete (22): Orange solid. M.p. 213–2158 (hexane/CH Cl ). IR (KBr):
2
2
1
3
7
070w, 3051w, 1456w, 1437s, 1336s, 1297m, 1254m, 1127w, 1059w, 1015w, 952w, 742vs, 723s. H-NMR:
13
.10–7.50 (m, 3 H); 7.70–7.80 (m, 1 H). C-NMR: 142.3, 133.4, 133.1 (3 C); 125.0, 124.9, 124.0, 121.6
+
(
4 CH). MS: 240 (100, M ). Anal. calc. for C H S (240.35): C 69.96, H 3.35, S 26.68; found: C 69.99,
14 8 2
H 3.28, S 26.51.
3
H-1,2-Benzodithiole-3-thione (23): Yellow solid. M.p. 95–978 ([21]: 988). Spectral data: identical
with those in [21].
N-(3H-1,2-Benzodithiol-3-ylidene)prop-1-en-2-amine (24): Oil. IR (neat): 3091w, 3062w, 2976w,
2
1
953w, 2921w, 2850w, 1632m (C=N), 1589m, 1469s, 1456s, 1447m, 1362m, 1322m, 1221s, 1165m,
076m, 908m, 809m, 783m, 742vs. H-NMR: 2.25–2.32 (m, 3 H); 5.53–5.68 (m, 2 H); 7.33–7.55 (m, 2
1

Helvetica Chimica Acta – Vol. 89 (2006)
999
1
3
H); 7.80–7.96 (m, 1 H); 8.10–8.25 (m, 1 H). C-NMR: 22.3 (Me); 117.8 (=CH ); 119.7, 124.7, 124.9,
1
2
+
27.2 (4 C); 133.5, 139.7, 153.1 (3 C); 165.3 (C=N). MS: 207(3, M ), 175 (57), 153 (34), 149 (41), 136
(
38), 89 (54), 77 (100).
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Received December 22, 2005