Spiro-λ4-sulfanes with intramolecular sulfur-oxygen interactions: Syntheses and molecular structures

Article abstract of DOI:10.1016/S0022-2860(97)00098-7

Three novel N-acetylated spiro-λ⁴-sulfanes with five-membered spirorings (fused with aromatic rings) and with two N heteroatoms (in (1)) or with N and O heteroatoms (in (2) and (3)) in axial positions have been prepared and their molecular structures determined by X-ray diffraction. The molecular structures of compounds (1-3) show trigonal bipyramidal geometry about the central sulfur atom. The rather long axial S-N bonds(1.93 A)in he symmetric spiro-λ⁴-sulfane (1) exhibit the usual hypervalent character, whereas the S-N (1.73 and 1.80 A) and S-O (2.23 and 2.07 A) bond lengths in the unsymmetric spiro λ⁴-sulfanes (2) and (3) correspond to elongated covalent S-N bonds and highly polarized S-O hypervalent bonds, respectively. Each structure exhibits usual S-C(ar) bond lengths (1.79-1.81 A). The axial N-S-N/O and the equatorial C(ar)-S-C(ar) angles lie in the intervals 173-179°and 98-103°, respectively. The conformations of (1-3) including the single-cis-single-trans isomerism of the endocyclic and exocyclic amide parts, the shape of the spirorings, and the relative positions of the equatorial aromatic rings are discussed in detail. In (1-3) the exocyclic carbonyl-oxygen approaches the central sulfur atom by 2.90,2.73 and 2.71 A, respectively, leading to an effective intramolecular sulfur-oxygen interaction of 1,4-type. The S···O close contacts, however, do not alter appreciably the trigonal bipyramidal geometry about the central sulfur atom.

Full text of DOI:10.1016/S0022-2860(97)00098-7

MOLSTR 9849
Journal of Molecular Structure 415 (1997) 1–16
Spiro-l4-sulfanes with intramolecular sulfur–oxygen interactions:
Syntheses and molecular structures
D. Szabo´a *, M. Kutia, I. Kapovitsa, J. Ra´baia,
A. Kucsman , Gy. Argay , M. Czugler , A. Ka´lma´n , L. Pa´rka´nyi
,
a
b
b
b
b
´
aDepartment of Organic Chemistry, Eo¨tvo¨s University, P.O. Box 32, H-1518 Budapest 112, Hungary
bCentral Research Institute of Chemistry, Hungarian Academy of Sciences, P.O. Box 17, H-1525 Budapest, Hungary
Received 13 February 1997; accepted 7 March 1997
Abstract
Three novel N-acetylated spiro-l4-sulfanes with five-membered spirorings (fused with aromatic rings) and with two N
heteroatoms (in (1)) or with N and O heteroatoms (in (2) and (3)) in axial positions have been prepared and their molecular
structures determined by X-ray diffraction. The molecular structures of compounds (1–3) show trigonal bipyramidal geometry
4
˚
about the central sulfur atom. The rather long axial S–N bonds (1.93 A) in the symmetric spiro-l -sulfane (1) exhibit the usual
˚
˚
hypervalent character, whereas the S–N (1.73 and 1.80 A) and S–O (2.23 and 2.07 A) bond lengths in the unsymmetric spiro-
l4-sulfanes (2) and (3) correspond to elongated covalent S–N bonds and highly polarized S–O hypervalent bonds, respectively.
˚
Each structure exhibits usual S–Car bond lengths (1.79–1.81 A). The axial N-S-N/O and the equatorial Car-S-Car angles lie in
the intervals 173–179Њ and 98–103Њ, respectively. The conformations of (1–3) including the single-cis–single-trans isomerism
of the endocyclic and exocyclic amide parts, the shape of the spirorings, and the relative positions of the equatorial aromatic
rings are discussed in detail. In (1–3) the exocyclic carbonyl-oxygen approaches the central sulfur atom by 2.90, 2.73 and 2.71
…
˚
A, respectively, leading to an effective intramolecular sulfur–oxygen interaction of 1,4-type. The S O close contacts, how-
ever, do not alter appreciably the trigonal bipyramidal geometry about the central sulfur atom. ᭧ 1997 Elsevier Science B.V.
Keywords: Hypervalent bonds; Spiro-l4-sulfanes; Sulfur–oxygen interaction; X-ray diffraction
1. Introduction
Stable spiro-l4-sulfanes are excellent models for
studying hypervalent bonding systems about the sul-
fur atom. The comparison of compound (4), the first
known representative of symmetric spiro-l4-sulfanes
[5], with its aza-analogue (5) [6] reveals that the S–X
hypervalent bonds in a symmetric axial X–S–X
moiety (XyO or N) are ‘‘balanced’’ and, as in the
case of S–X covalent single bonds, they are controlled
by the nature of the axial heteroatoms, as shown by
In continuation of our preceding studies on spiro-
l4-sulfanes (earlier spirosulfuranes) substituted sym-
metrically or unsymmetrically at axial positions [1–3],
we now report on the syntheses and molecular struc-
tures of the spiro-l4-sulfanes (1–3) with intramolecular
sulfur–oxygen interaction of 1,4-type [4].
˚
the bond length data r[S–O(acyloxy)] = 1 84 A in (4)
* Corresponding author.
0022-2860/97/$17.00 Copyright ᭧ 1997 Elsevier Science B.V. All rights reserved
PII S0022-2860(97)00098-7

2
D. Szabo´ et al./Journal of Molecular Structure 415 (1997) 1–16
covalent single bond, as can be seen, for example,
˚
from r[S–N(acylamino)] = 1 73 A in (6) [2]. In
contrast, the S–Y hypervalent bond with a more
electronegative heteroatom is dramatically polarized:
˚
in the same compound r[S–O(acyloxy)] = 2 13 A.
Nevertheless, the polarized (weak) hypervalent
bond can be well differentiated from an effective
…
S
O close contact which may be regarded as a
‘‘premature’’ hypervalent bond (see Ref. [8]). In the
acylaminosulfonium salt (7), for example, which is
…
stabilized by an intramolecular S O(carbamoyl)
…
close contact, a significantly longer r(S O) =
˚
2.37 A interatomic distance was determined [2].
By studying the molecular structures of spiro-l4-
sulfanes (1–3) the following questions are to be
answered: (i) how the hypervalent S–N bonds in
symmetric spiro-l4-sulfanes are affected by an
exocyclic N-alkyl → N-acyl change, i.e. by an
increase of the electronegativity of the axial nitrogen
atoms; (ii) how the N–S–O bonding system in
unsymmetric spiro-l4-sulfanes is affected by an
˚
˚
and r[S–N(acylamino)] = 1 90 A in (5) (cf. the sum of
˚
the covalent radii, S–O = 1 70 A and S–N = 1 74 A in
Ref. [7]).
(endo-carbonyl)–(exo-methyl)
→
(endo-methy-
lene)–(exo-carbonyl) change in the spirocyclic ring
system; (iii) whether or not the weakened axial S–O
hypervalent bond in unsymmetric spiro-l4-sulfanes is
altered by an increase of the axial S–N bond length
associated with steric constraint; (iv) whether or not
an exocyclic N-alkyl → N-acyl change results in the
…
formation of an intramolecular S O close contact,
and in the former case how the usual trigonal
bipyramidal geometry of the spiro-l4-sulfanes is
affected by the coordination of nonbonded oxygen
atom(s) to the central sulfur atom.
On the other hand, in unsymmetric spiro-l4-sul-
fanes with an axial X–S–Y moiety the bond strengths
reflected by the corresponding bond lengths are
‘‘disproportionated’’. The S–X bond with a less elec-
tronegative X heteroatom is practically as strong as a
1.1. Model compounds
In the synthesis of spiro-l4-sulfane (1) (Scheme 1),

3
D. Szabo´ et al./Journal of Molecular Structure 415 (1997) 1–16
Scheme 1. Synthesis of compound (1). Reagents and conditions:
(i) SOCl2, reflux, 2 h, then aq. NH3; (ii) Ac2O, drop of conc.
H2SO4, 140 ЊC, 3 min; (iii) TsNCl2, pyridine, 20 ЊC, 12 h.
2,2Ј-thiodibenzoic acid [9] (8) was first converted
into 2,2Ј-thiodibenzamide (9) through the corre-
sponding acid chloride (path i). The diamide (9)
obtained was acetylated with AC2O to (10) (path ii),
which was then oxidized with dichloramine-T
(TsNCl2) under anhydrous conditions to give (1)
(path iii).
Scheme 2. Synthesis of compound (2). Reagents and conditions:
(i) SOCl2, reflux, 2 h, then aq. NH3; (ii) aq. NaOBr and NaOH,
80 ЊC, 2 min, then AcOH-Ac2O, reflux, 5 min; (iii) Cu2O, pyridine,
reflux, 2 h; (iv) PTAB, pyridine-water, 20 ЊC, 1 h; (v) Ac2O,
pyridine, 100 ЊC, then cooling to 20 ЊC.
The synthesis of spiro-l4-sulfane (2) (Scheme 2)
started from (2-iodophenyl)acetic acid [10] (11)
which was treated with SOCl2, then with NH3 to
give (2-iodophenyl)acetamide (12) (path i). From
amide (12) the 2-iodo derivative of N-acetylbenzyl-
amine (13) was obtained by Hofmann rearrangement
followed by N-acetylation with AC2O (path ii). For
the preparation of sulfide (15) thiosalicylic acid
(14) was coupled with (13) (path iii). The treatment
of (15) with phenyltrimethylammonium tribromide
(PTAB) resulted in sulfoxide (16) (path iv), which
was dehydrated with AC2O to yield spiro-l4-sulfane
(2) (path v).
Spiro-l4-sulfane (3) was prepared from sulfide (17)
[11] by using dichloramine-T as oxidizing agent
(Scheme 3; path i).
Scheme 3. Synthesis of compound (3). Reagents and conditions: (i)
TsNCl2, pyridine, 0 ЊC, 12 h.

4
D. Szabo´ et al./Journal of Molecular Structure 415 (1997) 1–16
2. Experimental details
over P2O5 or KOH pellets, depending on the solvent
used.
2.1. Materials
2.2. 2,2Ј-diacetyl-1,1Ј-spirobi[3H-2,1-benzazathiole]
(1)
Melting points were determined on a Boetius micro
melting point apparatus. IR spectra were taken on a
Specord IR 75 (Zeiss, Jena) spectrophotometer.
Microanalyses were carried out in the microanalytical
laboratory of this department by Dr. H. Medzihradszky-
Schweiger and co-workers.
Solvents were purified and dried by the usual
methods. The evaporations were carried out under
reduced pressure. Products obtained from reaction
mixtures or by crystallization were dried in vacuo
2.2.1. Path (i) in Scheme 1
To 2,2Ј-thiodibenzoic acid [9] (8; 32.1 g, 0.117 mol)
was added 53 ml (0.73 mol) of thionyl chloride and
the reaction mixture was refluxed for 2 h, then the
excess of thionyl chloride was removed by evapora-
tion. The crude acid chloride residue was dissolved in
dry dioxane (150 ml), and 120 ml of aqueous NH3
was added dropwise to the stirred solution at room
Table 1
Crystal and relevant X-ray data for compounds (1–3)
Compound
(1)
(2)
(3)
Formula
MW
C18H14N2O4S
354.37
0 15 × 0 35 × 0 35
tetragonal
I43
12.596(1)
12.596(1)
10.278(1)
90
90
90
1630.7(2)
4
1.44
C16H1 3NO3S
299.35
0 13 × 0 16 × 0 30
monoclinic
P21/c
7.872(1)
13.340(1)
13.463(1)
90
97.95(1)
90
1400.2(4)
4
C19H13NO3S
335.38
0 18 × 0 20 × 0 25
triclinic
P −1
7.665(1)
8.031(1)
12.448(1)
105.1(1)
95.17(1)
94.71(1)
732.3(3)
2
Crystal size (mm)
Crystal system
Space group
˚
a (A)
˚
b (A)
˚
c (A)
a (Њ)
b (Њ)
g (Њ)
3
˚
V (A )
Z
Dc alc (g cm−3
F (000)
)
1.42
624
1.52
348
736
Temperature (K)
Scan mode
293(2)
q/2v
295(2)
q/2v
296(2)
q/2v
Scan rate (deg/min)
X-ray radiation
1–20
1–20
1–20
Cu Ka
1.54184
2.00
Cu Ka
1.54184
2.09
Mo Ka
0.71073
0.23
˚
l (A)
m (mm−1
)
v range (Њ)
1.5–75.0
888
1.5–75.0
2881
2481
1.5–30.0
4265
3054
Total reflections
Nonzero reflections
Refinement on
886
F2
F
F
Parameters refined
j level
117
2.0
191
3.0
269
3.0
R = SDF SFO
0.037
0.093
0.038
1.20
0.001
0.23
0.042
0.077
0.052
2.73
0.068
l0.23l
0.034
0.037
0.073
0.46
0.078
l0.26l
Rw = Sw(DF2) SlFO2 l
R indices (all data)
S = S(wkFOl − lFCk2) (NO − P)1
Max. (D j)
2
−3
˚
˚
Drmax (e.A
)
−3
Drmin (e.A
)
−0.23

5
D. Szabo´ et al./Journal of Molecular Structure 415 (1997) 1–16
Fig. 1. Perspective view of spiro-l4-sulfane (1) with numbering scheme for nonhydrogen atoms.
temperature. After standing overnight the solvent was
removed in vacuo, the residue was triturated with
water (100 ml), filtered and dried to yield 2,2Ј-thiodi-
benzamide (9; 29.7 g, 93%); after crystallization from
MeOH, m.p. 209–210 ЊC (207–209 ЊC in Ref. [12]).
calculated for C18H16N2O4S (356.4), C 60.66, H 4.52,
N 7.86, O 17.96, S 9.00%; found, C 60.3, H 4.4, N 7.7,
O 17.9, S 8.7%.
2.2.3. Path (iii) in Scheme 1
To a solution of (10) (1.05 g, 3 mmol) in dry
pyridine (10 ml) dichloramine-T (TsNCl2; 0.39 g,
1.6 mmol) was added and the reaction mixture was
allowed to stand at room temperature overnight. The
crystals of spiro-l4-sulfane (1) were filtered off,
washed with dry pyridine, acetone and ether, then
dried. Yield: 0.33 g (31%), m.p. 222–228 ЊC. IR
(KBr): 1690vs, 1660vs (CyO) cm−1. Elemental
analysis: calculated for C18H14N2O4S (354.4), C
61.01, H 3.98, N 7.90, O 18.07, S 9.05%; found, C
60.4, H 4.0, N 7.9, O 17.9, S 9.0%.
2.2.2. Path (ii) in Scheme 1
The mixture of diamide (9) (12 g, 0.044 mol),
Ac2O (33 ml, 0.352 mol) and 0.2 ml of concentrated
H2SO4 was heated in an oil bath at 140 ЊC for 3
minutes then poured into crushed ice (250 g). The
precipitate was filtered off, washed with water and
dried to give N,NЈ-diacetyl-2,2Ј-thiodibenzamide
(10; 14.4 g, 92%), m.p. 190–194 ЊC (after crystalliza-
tion from AcOH-H2O). IR (KBr): 3255s, 3170m
(NH), 1730vs, 1695s (CyO) cm−1. Elemental analysis:

6
D. Szabo´ et al./Journal of Molecular Structure 415 (1997) 1–16
Table 2
2
˚
Fractional atomic coordinates and mean equivalent isotropic displacement parameters Ue q (A ) for nonhydrogen atoms in compounds (1–3)
with ESDs in parentheses. Ue q is defined as 1/3 of the trace of the orthogonalized Uij tensor
Atom
x a
y b
z c
Ueq
Compound (1)
S(1)
O(1)
O(2)
N(1)
C(1)
C(2)
C(3)
C(4)
C(5)
C(6)
C(7)
C(8)
0
0
0.0000(1)
−0.0854(3)
0.1376(3)
0.029(1)
0.045(1)
0.056(1)
0.032(1)
0.032(1)
0.035(1)
0.045(1)
0.054(1)
0.051(1)
0.040(1)
0.032(1)
0.037(1)
0.046(1)
−0.1385(2)
0.1142(2)
−0.0203(2)
−0.1112(2)
−0.1554(2)
−0.2401(3)
−0.2794(3)
−0.2347(3)
−0.1507(3)
−0.1070(2)
0.0365(3)
0.0004(3)
−0.2765(2)
−0.1653(2)
−0.1515(2)
0.0058(2)
−0.0918(2)
−0.1004(3)
−0.0087(3)
0.0893(3)
0.0979(3)
−0.1864(2)
−0.2081(3)
−0.3157(3)
−0.0046(3)
−0.1111(3)
−0.1391(3)
−0.2252(4)
−0.2822(5)
−0.2533(5)
−0.1674(4)
−0.0745(3)
0.0891(3)
C(9)
0.1260(4)
Compound (2)
S(1)
O(1)
O(2)
O(3)
N(1)
C(1)
C(2)
C(3)
C(4)
C(5)
C(6)
C(7)
C(8)
C(9)
C(10)
C(11)
C(12)
C(13)
C(14)
C(15)
C(16)
0.0783(1)
0.2985(3)
0.1429(2)
−0.1217(2)
0.0265(2)
0.1762(3)
0.1770(3)
0.2504(4)
0.3231(3)
0.3205(4)
0.2456(3)
0.0944(4)
0.2636(3)
0.3351(3)
0.4784(3)
0.5502(3)
0.4761(3)
0.3301(3)
0.2540(3)
−0.0841(3)
−0.1523(4)
−0.1870(1)
−0.4169(1)
−0.2802(1)
−0.2463(2)
−0.1137(1)
−0.0791(2)
0.0030(2)
0.0919(2)
0.0959(2)
0.0131(2)
−0.0763(2)
−0.0119(2)
−0.2517(2)
−0.3258(2)
−0.3767(2)
−0.3508(2)
−0.2779(2)
−0.2274(2)
−0.3451(2)
−0.1583(2)
−0.0947(3)
−0.0971(1)
0.0820(1)
0.0406(1)
−0.2691(2)
−0.2027(1)
−0.0335(2)
−0.0955(2)
−0.0564(2)
0.0421(2)
0.1035(2)
0.0674(2)
−0.2011(2)
−0.1318(2)
−0.0665(2)
−0.0894(2)
−0.1748(2)
−0.2380(2)
−0.2186(2)
0.0267(2)
−0.2780(2)
−0.3652(2)
0.037(2)
0.075(1)
0.053(1)
0.065(1)
0.042(1)
0.038(1)
0.041(1)
0.055(1)
0.058(1)
0.057(1)
0.048(1)
0.050(1)
0.036(1)
0.040(1)
0.049(1)
0.057(1)
0.051(1)
0.041(1)
0.047(1)
0.051(1)
0.074(1)
Compound (3)
S(1)
O(1)
O(2)
O(3)
N(1)
C(1)
C(2)
C(3)
C(4)
C(5)
C(6)
C(7)
0.2229(1)
0.5082(3)
0.2867(2)
0.1005(2)
0.1665(2)
0.2695(2)
0.3291(3)
0.3564(3)
0.3226(3)
0.2178(3)
0.1625(3)
0.1434(3)
0.1772(2)
0.2718(1)
0.7407(2)
0.5300(2)
0.1381(2)
0.0441(2)
0.2154(2)
0.3242(2)
0.2506(3)
0.0770(3)
−0.2189(3)
−0.3139(3)
−0.2407(2)
−0.0647(2)
0.2475(1)
0.3230(1)
0.2552(1)
0.4081(1)
0.2335(1)
0.1046(1)
0.0446(2)
−0.0673(2)
−0.1165(2)
−0.0993(2)
−0.0303(2)
0.0836(2)
0.1257(1)
0.0314(1)
0.0633(8)
0.0471(6)
0.0467(6)
0.0311(5)
0.0319(6)
0.0412(7)
0.0476(8)
0.0448(8)
0.0429(8)
0.0447(8)
0.0394(7)
0.0298(6)
C(8)

7
D. Szabo´ et al./Journal of Molecular Structure 415 (1997) 1–16
Table 2 Continued
Atom
x a
y b
0.0360(2)
z c
0.0561(1)
Ueq
C(9)
0.2349(2)
0.2587(2)
0.4376(2)
0.5292(2)
0.6927(3)
0.7629(3)
0.6703(3)
0.5053(2)
0.4409(3)
0.0919(2)
0.0086(3)
0.0295(6)
0.0355(7)
0.0288(6)
0.0332(6)
0.0416(8)
0.0452(8)
0.0407(7)
0.0323(6)
0.0414(7)
0.0347(6)
0.0453(8)
C(10)
C(11)
C(12)
C(13)
C(14)
C(15)
C(16)
C(17)
C(18)
C(19)
−0.0374(2)
0.2952(2)
0.4597(2)
0.4924(3)
0.3611(3)
0.1984(2)
0.1635(2)
0.5924(2)
0.0159(2)
−0.1605(3)
−0.0566(1)
0.3263(1)
0.3505(1)
0.4127(2)
0.4495(2)
0.4250(2)
0.3631(1)
0.3083(2)
0.3252(1)
0.3208(2)
2.3. Spiro[3H-2,1-benzoxathiole-3Ј-one-1,1Ј-3H-2-
acetyl-2,1-benzazathiole] (2)
washed with water and dried to give N-(2-iodobenzyl)-
acetamide (13; 13 g, 42%), m.p. 129–133 ЊC (134–
135 ЊC in Ref. [13]).
2.3.1. Path (i) in Scheme 2
The mixture of (2-iodophenyl)acetic acid [10] (11;
65.5 g, 0.25 mol) and thionyl chloride (36 ml, 0.5 mol)
was refluxed for 2 h, then the excess of thionyl
chloride was removed in vacuo. The crude acid
chloride was dissolved in dioxane (50 ml) and the
solution was added dropwise to aqueous NH3
(150 ml) at room temperature. After standing over-
night the reaction mixture was evaporated, the residue
was triturated with water (100 ml), filtered and dried.
The crude (2-iodophenyl)acetamide (12) was crystal-
lized from EtOH, yielding 35.2 g (54%) of pure product,
m.p. 180–182 ЊC. IR (KBr): 3480–3250br (NH),
1660vs (CyO) cm−1. Elemental analysis: calculated for
C8H8INO (261.1), C 36.80, H 3.09, I 48.60, N 5.36, O
6.13%; found, C 36.5, H 3.0, I 48.4, N 5.4, O 6.1%.
2.3.3. Path (iii) in Scheme 2
A mixture of (13) (13 g, 0.047 mol), thiosalicylic
acid (14; 7.3 g, 0.047 mol) and Cu2O (3 g, 0.023 mol)
in dry pyridine (80 ml) was refluxed under N2 (2 h)
and, after cooling to room temperature, was poured
into a mixture of ice (300 g) and concentrated aqueous
HCl (150 ml). The precipitate was filtered off, washed
with water, then heated with a solution of Na2CO3
(5 g) in water (100 ml) at 100 ЊC (1 h). After filtration
the filtrate was cooled and acidified with concentrated
aqueous HCl (pH 1) under external ice-water cooling.
The solid product was filtered off, washed with water
and dried; the crude 2-[2-(acetylaminomethyl)phenyl-
thio]benzoic acid (15; 10.4 g, 74%) was crystallized
from EtOH, m.p. 182–183 ЊC. IR (KBr): 3295s (NH),
3360–2100br (OH), 1682vs, 1655vs (CyO) cm−1.
Elemental analysis: calculated for C16H15NO3S
(301.4), C 63.76, H 5.02, N 4.65, O 15.93, S
10.64%; found C 63.8, H 5.1, N 5.0, O 16.2, S 10.9%.
2.3.2. Path (ii) in Scheme 2
To a cold (0 ЊC) solution of NaOH (21 g, 0.52 mol)
in 84 ml of water was first added bromine (5.9 ml,
0.11 mol) then amide (12) (29.4 g, 0.112 mol) and
15.4 g (0.38 mol) NaOH in 56 ml of water. After
vigorous stirring for 15 minutes the reaction
mixture was heated to 80 ЊC for 2 minutes, then the
crude 2-iodobenzylamine product was isolated by
steam distillation followed by extraction with ether
(150 ml). After evaporation the residue was dissolved
in the mixture of AcOH (35 ml) and Ac2O (7 ml) then
refluxed for 5 minutes. The solution was poured into
cold water (200 ml), the precipitate was filtered off,
2.3.4. Path (iv) in Scheme 2
To a solution of sulfide (15) (0.53 g, 1.8 mmol) in
3.5 ml of pyridine and 0.2 ml of water was added
phenyltrimethylammonium tribromide (PTAB; 0.66 g,
1.8 mmol). The mixture was stirred at room tempera-
ture for 1 h then poured into ice-cold 2N H2SO4
(50 ml). After standing overnight (4 ЊC) the precipi-
tate formed was filtered off, washed with cold water
and dried to give 2-[2-(acetylaminomethyl)phenyl-

8
D. Szabo´ et al./Journal of Molecular Structure 415 (1997) 1–16
Table 3
a
Relevant geometric parameters for compound (1) with ESDs in parentheses
˚
Interatomic distances (A)
Spiroring
S(1) O(2)
S(1)–N(1)
S(1)–C(1)
C(1)–C(2)
C(2)–C(7)
A
A
…
2.899(3)
1.926(3)
1.809(3)
1.380(4)
1.494(4)
C(7)–N(1)
C(7)–O(1)
C(8)–N(1)
C(8)–C(9)
C(8)–O(2)
1.379(4)
1.207(4)
1.396(4)
1.479(5)
1.224(5)
Bond angles (Њ)
Spiroring
A
Exocyclic part
C(8)-N(1)-S(1)
C(2)-C(7)-O(1)
O(1)-C(7)-N(1)
C(7)-N(1)-C(8)
N(1)-C(8)-C(9)
N(1)-C(8)-O(2)
O(2)-C(8)-C(9)
A
N(1)-S(1)-N(1a)
N(1)-S(1)-C(1)
S(1)-C(1)-C(2)
C(1)-C(2)-C(7)
C(2)-C(7)-N(1)
C(7)-N(1)-S(1)
N(1)-S(1)-C(1a)
C(1)-S(1)-C(1a)
177.2(2)
85.5(2)
114.1(4)
116.9(4)
107.5(4)
115.7(3)
92.7(2)
101.7(2)
114.9(4)
125.0(5)
127.5(5)
127.1(5)
119.2(5)
117.8(5)
123.0(6)
…
S
O close contact
A
A
…
…
O(2) S(1)-N(1)
O(2) S(1)-C(1)
O(2) S(1) O(2a)
50.7(2)
136.2(2)
121.6(1)
O(2) S(1)-N(1a)
131.1(2)
84.0(2)
73.8(4)
…
…
O(2) S(1)-C(1a)
…
…
…
S(1) O(2)-C(8)
Torsion angles (Њ)
Spiroring
A
Aromatic ring position
C(2)-C(1)-S(1)-C(1a)
C(2)-C(1)-S(1)-N(1a)
C(6)-C(1)-S(1)-C(1a)
C(6)-C(1)-S(1)-N(1a)
A
S(1)-C(1)-C(2)-C(7)
C(1)-C(2)-C(7)-N(1)
C(2)-C(7)-N(1)-S(1)
C(7)-N(1)-S(1)-C(1)
N(1)-S(1)-C(1)-C(2)
0.5(3)
−3.9(4)
2.1(3)
−4.7(3)
2.1(3)
94.0(3)
179.9(3)
−85.1(4)
0.8(4)
Acylamino part
A
A
C(1)-C(2)-C(7)-O(1)
S(1)-N(1)-C(7)-O(1)
C(2)-C(7)-N(1)-C(8)
O(1)-C(7)-N(1)-C(8)
177.4(5)
−175.9 (7)
167.2(6)
−14.2(6)
C(7)-N(1)-C(8)-C(9)
C(7)-N(1)-C(8)-O(2)
S(1)-N(1)-C(8)-C(9)
S(1)-N(1)-C(8)-O(2)
−3.2(5)
177.2(6)
158.6(7)
−21.0(4)
…
S
O close contact
A
…
N(1)-C(8)-O(2) S(1)
C(8)-O(2) S(1)-N(1)
O(2) S(1)-N(1)-C(8)
13.0(3)
−10.7(4)
10.0(3)
…
…
a N(1a), O(1a), O(2a) and C(1a)–C(7a) are generated atoms.
sulfinyl]benzoic acid (16; 0.48 g, 86%), m.p. 221–
223 ЊC. IR (KBr): 3270s (NH), 1695s, 1615s (CyO),
1715vs (SyO) cm−1. Elemental analysis: calculated
for C16H15NO4S (317.4), C 60.55, H 4.76, N 4.41,
O 20.16, S 10.10%; found, C 60.7, H 4.9, N 4.2, O
20.1, S 10.0%.
2.3.5. Path (v) in Scheme 2
To a solution of sulfoxide (16) (0.32 g, 1 mmol) in
dry pyridine (2 ml) obtained by heating at 100 ЊC was
added Ac2O (1 ml), and the mixture was allowed to
cool to 20 ЊC. After standing for 12 h, the crystals of
spiro-l4-sulfane (2) were filtered off, washed with

9
D. Szabo´ et al./Journal of Molecular Structure 415 (1997) 1–16
Fig. 2. Perspective view of spiro-l4-sulfane (2) with numbering scheme for nonhydrogen atoms.
cold dry pyridine, acetone and ether, then dried.
Yield: 0.27 g (89%), m.p. 224–235 ЊC. IR (KBr):
1670vs, 1635vs, 1620vs (CyO) cm−1. Elemental ana-
lysis: calculated for C16H13NO3S (299.3), C 64.21,
H 4.38, N 4.68, O 16.04, S 10.71%; found, C 64.0,
H 4.3, N 4.9, O 16.4, S 11.0%.
C19H13NO3S (335.7), C 68.95, H 3.88, N 4.18,
O 14.31, S 9.55%; found, C 68.2, H 3.9, N 4.4,
O 13.9, S 9.4%.
2.5. Crystal structure determinations
Intensities for compounds (1) and (2) were recorded
on an Enraf Nonius CAD-4 diffractometer with
graphite monochromated Cu Ka radiation using q-2v
scan in the range 1 5 Ͻ v Ͻ 75Њ, whereas for com-
pound (3) monochromated Mo Ka radiation was
applied collecting data in the range 1 5 Ͻ v Ͻ 30Њ.
For each crystal three standard reflections were
monitored in every hour. No decay correction was
applied in either case. Cell constants (Table 1) for
each crystal were determined by least-squares refine-
ment of diffractometer angles for 25 automatically
centred reflections. Data were collected with the
Miller indices:
2.4. 2Ј-acetyl-[3H-2,1-benzoxathiole]-1,1Ј-spiro-
[2H-naphtho(1,8-c,d)isothiazole]-3-one (3)
2.4.1. Path (i) in Scheme 3
To a solution of 2-(8-acetylamino-1-naphthylthio)-
benzoic acid [11] (17; 0.17 g, 0.5 mmol) in dry pyri-
dine (0.4 ml) was added dichloramine-T (TsNCl2;
0.062 g, 0.26 mmol) at 0 ЊC. After standing overnight
the crystals were filtered off, washed with pyridine
and ether, then dried to give spiro-l4-sulfane (3)
(0.15 g, 90%) m.p. 237–239 ЊC. IR (KBr): 1653vs
(CyO) cm−1. Elemental analysis: calculated for

10
D. Szabo´ et al./Journal of Molecular Structure 415 (1997) 1–16
Fig. 3. Perspective view of spiro-l4-sulfane (3) with numbering scheme for nonhydrogen atoms.
Compound (1):
reflections with the criterion I Ͼ 3j for (2) and (3)
while for (1) Sw(DF2)2 was minimized for all unique
reflections by the program shelxl 93 [17] with the
− 15 Յ h Յ 15, 0 Յ k Յ 15, 0 Յ l Յ 12
Compound (2):
weighting
scheme
1 [j2(FO)2 +(0 0398P)2 +
1 0802P] where P =(FO2 +2FC2 ) 3. In each case, the
fractional coordinates of the hydrogen atoms were
generated from assumed geometries. The hydrogen
positions were refined isotropically for (1) and (3),
whereas in the case of (2) they were only included
0 Յ h Յ 9, 0 Յ k Յ 16, −16 Յ l Յ 16
Compound (3):
− 10 Յ h Յ 0, −11 Յ k Յ 11, −17 Յ l Յ 17
in the final structure factor calculations with mean
2
˚
Data were corrected for Lorentz and polarization
effects. The phase problems were solved by direct
methods using SHELX-76 [14] for (1) and program
multan [15] for (2) and (3).
For crystals (1) and (2) empirical absorption correc-
tions [16] were calculated at the end of the isotropic
least-squares refinement for the positional parameters
of nonhydrogen atoms. Full matrix least-squares refine-
ment minimized Sw(DF2) with w = 4FO2 j2(FO2 ) using
isotropic temperature factors BiH = BiC + 1 A to the
corresponding heavy atoms with isotropic displace-
ment parameters. Because (1) crystallized with the
polar space group I43 (No. 80) Flack parameter [18]
was refined to 0.02(4). Consequently, Fig. 1 depicts
the absolute configuration of the crystal specimen
mounted on the diffractometer. Scattering factors,
including corrections for anomalous dispersion, were
taken from standard tables [19]. Calculations for (1)

11
D. Szabo´ et al./Journal of Molecular Structure 415 (1997) 1–16
were carried out by the use of shelxl 93 [17] adapted
on a DEC5000 computer, while the calculations for (2)
and (3) were performed on a PDP 11/34 128 kw
minicomputer using SDP-plus and local programs.
Fractional coordinates and mean temperature fac-
tors (Ueq) with ESDs (estimated standard deviations)
in parentheses for nonhydrogen atoms in compounds
(1–3) are listed in Table 2. Because (1) has molecular
symmetry C2, coordinates are given in Table 2 only
for half of the molecule, and geometric parameters are
listed in Table 3 in the same way. Of course, the cross
angles (like Car-S-Car) as well as the corresponding
torsion angles are presented in Table 3.
elongation can be interpreted on the basis of Musher’s
theory [20] assuming hypervalent three-centre four-
electron bonds in the axial array. The slight increase
˚
3. Results and discussion
(0.03 A) in S–N bond lengths of (1) related to the
analogous bonds in (diacylamino)spiro-l4-sulfane
(5) [6] with alkyl-substituted axial nitrogen atoms
may be attributed to the somewhat different electro-
negativities of nitrogen atoms carrying an exocyclic
acetyl or alkyl substituent.
The perspective representations of spiro-l4-sul-
fanes (1–3) are shown in Fig. 1, Fig. 2 and Fig. 3,
and the relevant geometric parameters are summar-
ized in Table 3, Table 4 and Table 5.
As is expected from the known structure of spiro-
l4-sulfane (6) [2] with different (N and O) hetero-
atoms in axial positions, the axial S–N interatomic
distance in N-acetyl-substituted (alkylamino)(acyloxy)
spiro-l4-sulfane (2) corresponds to a slightly elong-
ated S–N covalent bond rather than a usual S–N
3.1. Sulfur configuration
As is known, spiro-l4-sulfanes exhibit almost per-
fect trigonal bipyramidal geometry with identical or
different atoms (X and Y = e.g. O or N) in axial posi-
tions. The X(axial)-S-Y(axial) bond angles are near
180Њ, and the X/Y(axial)-S-C(equatorial) bond angles
are practically rectangular, independent both of the
identity of heteroatoms and of the size of spirorings
[1,2,6]. This statement is true for the structures (1–3)
as well: the N-S-N or N-S-O bond angles are 177Њ,
179Њ and 177Њ, respectively. The endocyclic N-S-C or
O-S-C bond angles range from 81Њ to 89Њ, whereas the
exocyclic analogues are usually wider than 90Њ (89–99Њ).
The C(equatorial)-S-C(equatorial) bond angles in (1–3)
(c =102Њ, 101Њ and 103Њ, respectively) are somewhat
smaller than those found, for example, in the analo-
gous compounds (4–6) (c =104–107Њ).
˚
hypervalent bond (1.73 A in both (2) and (6)). On
the other hand, the S–O interatomic distances in
˚
˚
both compounds (2.13 A in (6) and 2.23 A in (2))
are significantly elongated compared with the usual
˚
hypervalent S–O bonds (1.84 A) found for example in
the symmetric (diacyloxy)spiro-l4-sulfane (4) [1].
Bond elongation points to a remarkably polarized
hypervalent S–O bond as shown by the predominant
limiting structure (2A) (cf. Refs. [2,4,8]).
The disproportion of the axial bond strengths may
be ascribed to the different electronegativity of the
˚
axial N and O heteroatoms. The r(N–S–O) =3 96 A
distance characterizing the axial array in (2) markedly
…
˚
differs from the analogous r(N–S O) =4 06 A dis-
tance observed [2] for the cyclic acylaminosulfonium
compound (7) which is stabilized by an intra-
3.2. Bond lengths about the central sulfur
In the symmetric (diacylamino)spiro-l4-sulfane (1)
molecular S O close contact arising from the
…
with acetyl-substituted nitrogen heteroatoms in axial
positions, the axial S–N bonds (1.93 A) are consider-
ortho-carbamoyl substituent. The comparison of
compounds (2) and (6) indicates that S–N bond
length does not depend on whether the endocyclic
methylenamino group is N-acetylated (in (2)) or the
˚
ably longer than the sum of the covalent radii of the S
˚
and N atoms (1.74 A [7]). As in other cases, the bond

12
D. Szabo´ et al./Journal of Molecular Structure 415 (1997) 1–16
Table 4
Relevant geometric parameters for compound (2) with ESDs in parentheses
˚
Interatomic distances (A)
Spirorings
S(1) O(3)
A
B
…
2.731(2)
1.727(2)
1.793(2)
1.378(3)
1.493(3)
1.458(3)
1.377(3)
1.487(4)
1.221(3)
S(1)–O(2)
S(1)–C(8)
C(8)–C(9)
C(9)–C(14)
C(14)–O(2)
C(14)–O(1)
2.231(2)
1.811(2)
1.390(3)
1.506(3)
1.263(3)
1.234(3)
S(1)–N(1)
S(1)–C(1)
C(1)–C(2)
C(2)–C(7)
C(7)–N(1)
C(15)–N(1)
C(15)–C(16)
C(15)–O(3)
Bond angles (Њ)
Spirorings
A
179.1(1)
88.6(2)
112.8(3)
115.7(3)
104.4(3)
118.1(2)
99.4(2)
B
N(1)-S(1)-O(2)
N(1)-S(1)-C(1)
S(1)-C(1)-C(2)
C(1)-C(2)-C(7)
C(2)-C(7)-N(1)
C(7)-N(1)-S(1)
N(1)-S(1)-C(8)
C(1)-S(1)-C(8)
O(2)-S(1)-C(8)
S(1)-C(8)-C(9)
C(8)-C(9)-C(14)
C(9)-C(14)-O(2)
C(14)-O(2)-S(1)
O(2)-S(1)-C(1)
81.4(1)
116.5(3)
117.9(3)
112.9(3)
110.0(2)
91.0(1)
101.4(2)
Exocyclic parts
C(7)-N(1)-C(15)
N(1)-C(15)-C(16)
N(1)-C(15)-O(3)
O(3)-C(15)-C(16)
C(15)-N(1)-S(1)
A
B
127.3(3)
117.2(4)
118.7(4)
124.1(4)
114.5(3)
C(9)-C(14)-O(1)
O(2)-C(14)-O(1)
121.1(4)
126.0(4)
…
S
O close contact
A
B
…
O(3) S(1)-N(1)
O(3) S(1)-C(1)
S(1) O(3)-C(15)
54.8(1)
142.8(1)
71.7(2)
O(3) S(1)-O(2)
O(3) S(1)-C(8)
125.6(1)
91.9(1)
…
…
Torsion angles (Њ)
Spirorings
A
B
S(1)-C(1)-C(2)-C(7)
C(1)-C(2)-C(7)-N(1)
C(2)-C(7)-N(1)-S(1)
C(7)-N(1)-S(1)-C(1)
N(1)-S(1)-C(1)-C(2)
1.4(2)
3.4(3)
− 7.3(2)
7.1(3)
S(1)-C(8)-C(9)-C(14)
C(8)-C(9)-C(14)-O(2)
C(9)-C(14)-O(2)-S(1)
C(14)-O(2)-S(1)-C(8)
O(2)-S(1)-C(8)-C(9)
− 0.4(2)
− 9.5(3)
12.5(2)
− 10.8(3)
5.4(2)
− 4.6(2)
Aromatic ring positions
C(2)-C(1)-S(1)-C(8)
C(2)-C(1)-S(1)-O(2)
C(6)-C(1)-S(1)-C(8)
C(6)-C(1)-S(1)-O(2)
A
B
94.7(2)
176.1(3)
− 85.0(2)
− 3.7(3)
C(9)-C(8)-S(1)-C(1)
C(9)-C(8)-S(1)-N(1)
C(13)-C(8)-S(1)-C(1)
C(13)-C(8)-S(1)-N(1)
94.6(3)
− 174.9(3)
− 84.9(3)
5.6(3)
Acylamino part
A
Acyloxy part
B
C(2)-C(7)-N(1)-C(15)
C(7)-N(1)-C(15)-C(16)
169.0(4)
− 4.4(4)
C(8)-C(9)-C(14)-O(1)
S(1)-O(2)-C(14)-O(1)
171.8(4)
− 168.8(7)

13
D. Szabo´ et al./Journal of Molecular Structure 415 (1997) 1–16
Table 4 Continued
˚
Interatomic distances (A)
C(7)-N(1)-C(15)-O(3)
S(1)-N(1)-C(15)-C(16)
S(1)-N(1)-C(15)-O(3)
176.4(4)
172.0(5)
− 7.2(3)
…
S
O close contact
A
…
N(1)-C(15)-O(3) S(1)
C(15)-O(3) S(1)-N(1)
O(3) S(1)-N(1)-C(15)
4.4(2)
− 3.7(3)
3.4(2)
…
…
˚
endocyclic carbonylamino group is N-methylated (in
(6)). This phenomenon may be explained by the fact
that the electronegativity of the axial nitrogen atoms
carrying an acyl, an alkyl and a sulfenyl substituent in
both cases is the same.
bond lengths (1.79–1.81 A) correspond to the usual
values observed for S(IV)–Car bonds.
3.3. Conformation of spiro-l4-sulfane rings
Formulae show that there is a structural analogy
between the N-acetyl-substituted (arylamino)(acyloxy)
spiro-l4-sulfane (3) and compound (2) with spiro-
cyclic (aralkylamino)(acyloxy) moieties and exocyc-
lic N-acetyl group. In the case of (3), however, the
axial S–N part is connected to the 1,8 (peri) position
of a naphthalene ring, which causes considerable
strain in the five-membered 1,2-thiaza spiroring. If
an idealized geometry of the naphthalene ring were
taken into account, the S–N distance would be
The 1,2-thiazoline spirorings (rings A) in spiro-l4-
sulfanes (1–3) are practically planar with maximum
torsion angles Jmax = 5Њ, 7Њ and 2Њ, respectively
(cf. Jmax = 16Њ in (5) and 6Њ in (6)). The endocyclic
amide parts in N-acetyl-substituted spiro-l4-sulfane
(1) are of single-trans conformation: (f(S − N − Cy
O) = −174Њ. The ‘‘endocyclic’’ C(7)yO(1) bond
˚
(1.21 A) is shorter, whereas the C(7)–N(1) bond is
˚
longer (1.38 A) than the corresponding bonds in the
N-alkyl-substituted spiro-l4-sulfane (5) (1.23 and
˚
˚
about 2.48 A, which is very far from the almost cova-
1.34 A). The difference may be explained by the
˚
lent S–N bond length of 1.73 A observed for the
fact that the lone pair of the nitrogen atom carrying
two acyl groups in compound (1) is less involved in
endocyclic amide conjugation than in the case of
monoacyl derivative (5).
spiro-l4-sulfanes (2) and (6) with axial N and O
heteroatoms. Nevertheless, the bond angle distortions
of the peri-substituted naphthalene ring in compound
(3) lead to a compromise: the axial nitrogen can
The 1,2-oxathiole spirorings (rings B) in spiro-l4-
sulfanes (2) and (3) are not far from being planar with
maximum torsion angles Jmax = 12Њ and 1Њ, respec-
tively (cf. Jmax = 6Њ in (4) and 16Њ in (6)). In com-
pounds (2) and (6) ring B assumes a flattened
envelope form with O(2) in (2) and S(1) in (6) on
the flap. Owing to the zwitterionic character of the
unsymmetric spiro-l4-sulfanes (2) and (3) as well as
that of the analogous compound (6) described earlier
[2], the CyO double bonds in acyloxy moieties are
˚
approach the central sulfur by 1.80 A. In the 1,2-
thiaza spiroring the actual bond angles involving the
naphthalene carbon atoms are 111Њ, 117Њ and 110Њ,
instead of the idealized 120Њ. The rather long
‘‘covalent’’ S–N bond in the naphthalene derivative
(3) is associated with a rather short ‘‘polarized hyper-
˚
valent’’ S–O bond (2.07 A), so that the r(N–S–O)
˚
distance of 3.87 A in (3) corresponds to the similar
values observed for other spiro-l4-sulfanes with axial
nitrogen and oxygen heteroatoms. S–N and S–O bond
lengths suggest that the zwitterionic character of
compound (3) (see the limiting structure (3A)) is
less pronounced than that of compound (2).
˚
longer (1.23, 1.22 and 1.21 A, respectively), whereas
the C–O single bonds are shorter (1.26, 1.29 and 1.29
˚
A, respectively) than the corresponding bonds in the
symmetric spiro-l4-(diacyloxy)-sulfane (4) with two
In spiro-l4-sulfanes (1–3) the equatorial S–Car
equivalent S–O hypervalent bonds (1.19 A for CyO
˚

14
D. Szabo´ et al./Journal of Molecular Structure 415 (1997) 1–16
Table 5
Relevant geometric parameters for compound (3) with ESDs in parentheses
Spirorings
˚
Interatomic distances (A)
S(1) O(3)
A
B
…
2.705(1)
1.804(1)
1.794(2)
1.402(2)
1.405(2)
1.411(2)
1.382(2)
1.491(2)
1.217(2)
S(1)–O(2)
2.066(1)
1.808(1)
1.389(2)
1.488(2)
1.294(2)
1.219(2)
S(1)–N(1)
S(1)–C(1)
C(1)–C(9)
C(8)–C(9)
C(8)–N(1)
C(18)–N(1)
C(18)–C(19)
C(18)–O(3)
S(1)–C(11)
C(11)–C(12)
C(12)–C(17)
C(17)–O(2)
C(17)–O(1)
Bond angles
Spirorings
A
177.2(1)
88.4(1)
111.0(2)
116.6(2)
109.6(2)
114.3(2)
97.6(1)
B
N(1)-S(1)-O(2)
N(1)-S(1)-C(1)
S(1)-C(1)-C(9)
C(1)-C(9)-C(8)
C(9)-C(8)-N(1)
C(8)-N(1)-S(1)
N(1)-S(1)-C(11)
C(1)-S(1)-C(11)
O(2)-S(1)-C(11)
S(1)-C(11)-C(12)
C(11)-C(12)-C(17)
C(12)-C(17)-O(2)
C(17)-O(2)-S(1)
O(2)-S(1)-C(1)
83.7(1)
114.7(2)
116.9(2)
111.6(2)
113.1(2)
88.9(1)
103.4(1)
Exocyclic parts
C(8)-N(1)-C(18)
N(1)-C(18)-C(19)
N(1)-C(18)-O(3)
O(3)-C(18)-C(19)
C(18)-N(1)-S(1)
A
B
132.5(2)
119.8(2)
117.7(2)
122.5(2)
112.1(2)
C(12)-C(17)-O(1)
O(2)-C(17)-O(1)
123.2(3)
125.3(3)
…
S
O close contact
A
B
…
O(3) S(1)-N(1)
O(3) S(1)-C(1)
S(1) O(3)-C(18)
54.9(1)
143.1(1)
74.5(2)
O(3)-S(1)-O(2)
O(3) S(1)-C(11)
127.8(1)
86.1(1)
…
…
…
Torsion angles (Њ)
Spirorings
A
B
S(1)-C(1)-C(9)-C(8)
C(1)-C(9)-C(8)-N(1)
C(9)-C(8)-N(1)-S(1)
C(8)-N(1)-S(1)-C(1)
N(1)-S(1)-C(1)-C(9)
− 1.7(2)
0.2(2)
1.4(1)
− 2.0(2)
2.0(2)
S(1)-C(11)-C(12)-C(17)
C(11)-C(12)-C(17)-O(2)
C(12)-C(17)-O(2)-S(1)
C(17)-O(2)-S(1)-C(11)
O(2)-S(1)-C(11)-C(12)
− 0.5(2)
0.8(2)
− 0.6(1)
0.3(2)
0.1(2)
Aromatic ring positions
C(9)-C(1)-S(1)-C(11)
C(9)-C(1)-S(1)-O(2)
C(2)-C(1)-S(1)-C(11)
C(2)-C(1)-S(1)-O(2)
A
B
99.5(2)
− 177.3(2)
− 81.1(2)
2.1(2)
C(12)-C(11)-S(1)-C(1)
C(12)-C(11)-S(1)-N(1)
C(16)-C(11)-S(1)-C(1)
C(16)-C(11)-S(1)-N(1)
87.5(2)
177.7(2)
− 94.4(2)
− 4.2(2)
Acylamino part
A
Acyloxy part
B
C(9)-C(8)-N(1)-C(18)
C(8)-N(1)-C(18)-C(19)
167.9(3)
2.8(2)
C(11)-C(12)-C(17)-O(1)
S(1)-O(2)-C(17)-O(1)
− 179.3(3)
179.4(5)

15
D. Szabo´ et al./Journal of Molecular Structure 415 (1997) 1–16
Table 5 Continued
Spirorings
C(8)-N(1)-C(18)-O(3)
S(1)-N(1)-C(18)-C(19)
S(1)-N(1)-C(18)-O(3)
− 178.6(3)
169.5(3)
− 11.9(2)
…
S
O close contact
A
…
N(1)-C(18)-O(3) S(1)
C(18)-O(3) S(1)-N(1)
O(3) S(1)-N(1)-C(18)
7.6(1)
− 6.3(2)
5.7(1)
…
…
4
˚
and 1.32 A for C–O). In unsymmetric spiro-l -
sulfanes the tendency of C–O bond equalization
resembles the carboxylate group.
by an irregular nonbonded coordination of the exocyclic
carbonyl-oxygens to the sulfur atom. The carbonyl-
oxygen approaching the central sulfur from the side of
the sulfur lone pair lies nearer to the ring AЈ or B
than to ring A, as shown by the angles cAЈ B
3.4. Orientation of aromatic rings
…
(Car − S O) =84Њ, 72Њ and 75Њ, and cA(Car −
…
The torsion angles J(Car − Car − S − Car) =94Њ, 95Њ
and 100/88Њ obtained for compounds (1), (2) and (3),
respectively, show that the aromatic rings fused with the
heterocyclic spirorings are nearly perpendicular to the
Car–S–Car plane, like other spiro-l4-sulfanes, e.g. (4),
(5) and (6) with J(Car − Car − S − Car) =96Њ, 100/80Њ
and 102Њ, respectively.
S
O) =136Њ, 143Њ and 143Њ, observed in compounds
…
(1), (2) and (3), respectively. The N-S O angles (51Њ,
55Њ and 55Њ, respectively) are far from being rec-
tangular, indicating that the exocyclic carbonyl-oxygen
rises markedly above the Car–S–Car equatorial plane.
In spiro-l4-sulfanes (1–3) the slight deviation of the
exocyclic torsion angles JA(S-N-CyO) from the J = 0
value, which would point to an ideal eclipsed confor-
mation, may be ascribed to a repulsion caused by the
…
3.5. Intramolecular S O close contacts
sulfur lone pair. Owing to the given position of the
The axial nitrogen atoms in spiro-l4-sulfanes (1–3)
bear an N-acetyl substituent. In all three cases the
exocyclic amide parts assume a near single-cis
conformation with the exocyclic torsion angles
J(S − N − CyO) = −21Њ, − 7Њ and − 12Њ, respectively.
The almost eclipsed conformations allow the central
sulfur and the exocyclic carbonyl-oxygen in (1), (2)
and (3) to approach one another by 2.90, 2.73 and
… …
exocyclic carbonyl-oxygens, the O S O angle in
the symmetric spiro-l4-sulfane (1) with two N-acetyl
groups is not linear but assumes a value of 122Њ.
˚
The C–N bond lengths (1.40, 1.38 and 1.38 A) in
the exocyclic amide part of spiro-l4-sulfanes (1–3)
are significantly greater than the average value of
˚
1.33 A obtained for N-substituted amides [10],
˚
whereas the CyO bond lengths (1.22 A for all) corre-
˚
˚
2.71 A, respectively, i.e. by a distance which is
spond to the expected value (1.23 A in Ref. [21]). It
much shorter than the sum of the van der Waals
seems very likely that the decrease of the conjugative
effect in the exocyclic amide part is associated with
the S O close contact involving the carbonyl-oxygen
˚
…
radii 3.25 A [7]. The relatively short S O distances
characterizing these particular cases of 1,4-type sul-
fur–oxygen nonbonded interaction may be ascribed to
a short ‘‘central’’ S–N bond (cf. Formula 45 and
Table 9 in Ref. [4]).
…
of the amide group.
Acknowledgements
As can be seen in Fig. 1, Fig. 2 and Fig. 3, the
trigonal bipyramidal geometry of the central sulfur
in spiro-l4-sulfanes (1–3) is not affected appreciably
This work was supported by the Hungarian Scien-
tific Research Foundation (OTKA, No. T017187).

16
D. Szabo´ et al./Journal of Molecular Structure 415 (1997) 1–16
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