Unexpected conversions of selected heteroorganic compounds

Article abstract of DOI:10.1002/hc.10077

A few unexpected conversions of selected heteroorganic compounds are described, including the formation of N-sulfonyl sulfenamide derivatives and the mixed phosphinyl-sulfenyl anhydrides in the reactions of sulfinyl chlorides with α-phenylethylamine or t-butyl-phenylphosphine oxide, respectively. Unexpected reactions of the ortho hydroxyalkyl-substituted diaryl sulfoxides and hypervalent sulfur and selenium derivatives, induced by triphenylphosphine, are also presented. Attempts to rationalize the observed reaction courses are briefly discussed.

Full text of DOI:10.1002/hc.10077

Heteroatom Chemistry
Volume 13, Number 5, 2002
Unexpected Conversions of Selected
Heteroorganic Compounds
Jo´zef Drabowicz
Department of Heteroorganic Chemistry, Center of Molecular and Macromolecular Studies,
"
Polish Academy of Sciences, 90-363 Lo´dz´, Sienkiewicza 112, Poland
Received 22 January 2002; revised 10 April 2002
of everyday laboratory work. In this account, a few
ABSTRACT: A few unexpected conversions of se-
such unexpected conversions of selected heteroor-
lected heteroorganic compounds are described, in-
ganic compounds are presented, together with at-
cluding the formation of N-sulfonyl sulfenamide
tempts to rationalize the observed reaction courses.
derivatives and the mixed phosphinyl-sulfenyl an-
Among them, we discuss the following:
hydrides in the reactions of sulfinyl chlorides with
-phenylethylamine or t-butyl-phenylphosphine ox-
ide, respectively. Unexpected reactions of the ortho
hydroxyalkyl-substituted diaryl sulfoxides and hyper-
(a) Formation of N-sulfonyl sulfenamide derivatives
by the condensation of sulfinyl chlorides with op-
tically active ␣-phenylethylamine;
valent sulfur and selenium derivatives, induced by
(b) The formation of mixed phosphinyl-sulfenyl
triphenylphosphine, are also presented. Attempts to ra-
anhydrides in the reaction of t-butylphenylphos-
tionalize the observed reaction courses are briefly dis-
phine oxide with sulfinyl chlorides;
C
cussed. 2002 Wiley Periodicals, Inc. Heteroatom Chem
(c) Unexpected reactions of the ortho hydroxyalkyl-
substituted diaryl sulfoxides.
13:437–442, 2002; Published online in Wiley Interscience
(www.interscience.wiley.com). DOI 10.1002/hc.10077
Some uncommon reactions of hypervalent sulfur
and selenium derivatives, induced by triphenylphos-
phine, are also presented.
INTRODUCTION
In spite of the fact that the recent enormous progress
in theory and experimental studies has made organic
chemistry a much more logical and predictable sub-
ject, unexpected conversions and observations how-
ever, made by serendipity still constitute a vital part
FORMATION OF N-SULFONYL
SULFENAMIDE DERIVATIVES BY THE
CONDENSATION OF SULFINYL CHLORIDES
WITH OPTICALLY ACTIVE
␣-PHENYLETHYLAMINE
A few experiments reported in this paper were realized in the
frame of the bilateral project entitled “Optically active heteroatom
derivatives with asymmetric center only at high coordinated het-
eroatoms: New synthetic approaches and comparative studies on
their racemization” supported by the Polish Academy of Sciences
and JSPS.
Correspondence to: Jo´zef Drabowicz; e-mail: draj@bilbo.cbmm.
lodz.pl.
Contract grant sponsor: State Committee for Scientific
Research.
A very clean formation of diastereomeric N-␣-
phenylethyl-p-toluenesulfinamides was found to oc-
cur in the reaction of p-toluenesulfinyl chloride with
optically active ␣-phenylethylamine [1]. A similar re-
action course was observed in the condensation of
adamantanesulfinyl chloride 1 with this same opti-
cally active amine 2, carried out in the presence of an
equivalent amount of triethylamine as an HCl scav-
Contract grant number: T09A 07714.
2002 Wiley Periodicals, Inc.
"
c
enger [2, J. Drabowicz, M. Mikolajczyk, manuscript
437

438 Drabowicz
SCHEME 3
It is evident from the results given in Table 1 that
the amount of the sulfenamide 7 formed is strongly
influenced by the nature of the tertiary amine used.
Simultaneously, this new asymmetric synthesis of
diastereomeric sulfinamides 6 is modestly efficient
in terms of chemical yields and diastereomeric
excess values. The de values of 6 were found to be
close to a 2:1 ratio. It should be noted here that, with
diisopropylethylamine and tetramethylethylenedi-
amine, exclusive formation of the sulfinamide 6 was
observed.
Exclusive and simultaneous formation of the
sulfenamides 4 or 7 in the reactions between
adamantanesulfinyl chloride 1 or t-butanesulfinyl
chloride 5 with optically active ␣-phenylethylamine
2 may be rationalized by the sequence of events
shown in Scheme 4.
Formation of the sulfenamide 4 or 7 is believed
to proceed in two steps. The initial step involves the
generation of the corresponding sulfinamide (3 or 6).
In the second step, the sulfinamide 3 or 6 reacts with
the appropriate sulfinyl chloride (1 or 5) to give the
aminosulfonium salt 8. Deprotonation of the salt 8
by an external base gives the ylide-like structures 9,
which finally rearranges to form the sulfenamide 4 or
7. This mechanistic proposal was strongly supported
by additional experiments which confirmed that the
sulfenamide 4 is formed in the reactions between
SCHEME 1
in preparation]. Moreover, the pure diasteoromers of
sulfinamide 3 were isolated by column chromatog-
raphy on silica gel (Scheme 1).
To find out whether the nature of the tertiary
amine used has an influence on the selectivity of this
condensation, an independent experiment, in which
triethylamine was replaced by pyridine, was carried
out. Its outcome was, however, completely unex-
pected. Instead of the expected diastereomeric sulfi-
namide 3 N-adamantanesulfonyl-N0-␣-phenylethyl-
adamantane-sulfenamide (4) was isolated as a single
reaction product (Scheme 2).
The structure of 4 is fully supported by elemen-
tal analysis and spectroscopic techniques, including
X-ray analysis. In a similar set of experiments, t-
butanesulfinyl chloride 5 was found to react with the
amine 2 in the presence of a variety of tertiary amines
(used as the HCl scavenger) with the simultaneous
formation of the expected sulfinamide 6 (as a mix-
ture of diastereomers) and N-t-butanesulfonyl N0-␣-
phenylethyl-t-butane sulfenamide (7) (Scheme 3 and
Table 1).
TABLE 1 Condensation of t-Butanesulfinyl Chloride (5) with
(-)- -Phenylethylamine 2 in the Presence of Tertiary Amines
6a,b
Base
Yield (%)
a/b Ratio
7
(-) Me2N PEA
iPr2NEt
TMEDA
53
85
90
68
29
48
82
7:3
30:12
16.2:7.7
18.7:10.8
15.6:9.7
13.4:8.5
2.0:1.0
27
0
0
21.0
40.0
32
4
K2CO3
2-MCHa
Et2NPh
4-Me2N-Pyridine
SCHEME 2
a2-MCH = 2-methylquinoline.

Unexpected Conversions of Selected Heteroorganic Compounds 439
electrophilic reagents to give the corresponding P O
derivatives without the loss of configurational in-
tegrity at phosphorus [3–6]. Similarly, additions of
elemental sulfur and selenium to enantiomeric phos-
phine oxides 10 in the presence of triethylamine
proceeds with a complete retention of configura-
tion at phosphorus and gives the enantiomeric phos-
phinothioic acid and phosphinoselenoic acids, re-
spectively [7,8].
With optically active 10 in hands (obtained via
formation of diastereomeric complexes with enan-
tiomers of mandelic acid [9,10]) we envisaged a pos-
sibility of the preparation of the mixed anhydrides 11
and 12 and their use as chiral substrates for the syn-
thesis of optically active sulfinyl derivative according
to the general reaction sequence shown in Scheme 6.
However, preliminary experiments (J. Drabow-
icz, unpublished results) carried out with equimo-
lar amounts of the oxide 10 and the t-butanesulfinyl
chloride 5 in the presence of pyridine have shown
that the expected anhydrides 11a and 11b were not
present in the postreaction mixture, from which
the mixed phosphinyl-sulfenyl anhydride 14 was
isolated in 85% yield. It was accompanied by t-
butylphenylphosphinyl chloride 15 and S-t-butyl-
t-butanethiosulfonate 16 (Scheme 7).
It is interesting to note that the anhydride 14
was simultaneously formed with the corresponding
sulfinyl-phosphinyl anhydride 17 in the reaction of
t-butanesulfinyl chloride 5 with t-butylphenylphos-
phinothioic acid 18 (Scheme 8). Formation of the
sulfenyl anhydride 14 results most probably from
the deoxygenation of the sulfinyl analogue 17 by t-
butanesulfinyl chloride with the simultaneous gen-
eration of t-butanesulfenyl chloride.
SCHEME 4
the diastereomerically pure sulfinamides 3a or 3b
and adamantanesulfinyl chloride 1 carried out in the
presence of pyridine (Scheme 5).
FORMATION OF THE MIXED PHOSPHINYL-
SULFENYL ANHYDRIDES IN THE
REACTIONS OF t-BUTYLPHENYLPHOS-
PHINE OXIDE WITH SULFINYL CHLORIDES
Among many substrates for the synthesis of a vari-
ety of enantiomerically pure compounds structurally
related to phosphine oxides, the enantiomeric forms
of the secondary tert-butylphenylphosphine oxide 10
are the most useful and promising ones. It was re-
cently reported that the lithiated derivatives of 10
are configurationally stable and react with various
SCHEME 5
SCHEME 6

440 Drabowicz
SCHEME 9
SCHEME 7
An unexpected course was found for the re-
action between the sodium salt of ( )-(S)-10 and
methyl bromoacetate in methanol [9]. This conver-
sion gave, not the expected alkylation product, but
rather ( )-(S)-methyl t-butylphenylphosphinate 25.
Its formation can be explained by the reaction se-
quence shown in Scheme 12.
Condensation of adamantanesulfinyl chloride 1
with the levorotatory enantiomer of the oxide 10
gave in 40% yield the sulfenyl-phosphinyl anhydride
20. It was accompanied by the phosphinyl chlo-
ride 15 and S-adamantyl adamantanethiosulfonate
21 (Scheme 9).
UNEXPECTED REACTIONS OF THE
ORTHOHYDROXYALKYL SUBSTITUTED-
DIARYL SULFOXIDES
In this context, it is interesting to note that
the similar condensation between the oxide 10 and
methanesulfinyl chloride 22 gave only the phos-
phinyl chloride 15 having the inverted configura-
tion at phosphorus, and even traces of the corre-
sponding sulfenyl-phosphinyl anhydride 23 could
not be detected among the crude reaction products
(Scheme 10).
By consideration of the chlorination ability of
sulfinyl chlorides toward the phosphine oxide 10, it
should be noted that this oxide upon dissolving in
carbon tetrachloride can be converted into the phos-
phinyl chloride 15, with very high stereoselectivity
[10]. This reaction is explained in Scheme 11. A sim-
ilar mechanism has been postulated earlier for the
acid-catalyzed exchange of the active hydrogens of
dialkyl phosphonates [11] and it seems possible that
the actual species reacting with halogen is the phos-
phite, trivalent tautomer [12].
Recently we prepared
a few optically active
aryl(alkyl) (ortho-hydroxyalkyl)aryl sulfoxides,
among them was di-trifluorohydroxymethyl ana-
logue 26, which was found to exist in solution in an
equilibrium with the corresponding hydroxysulfu-
rane structure 27 [13] (Scheme 13).
Most probably, because of the existence of this
equilibrium, we were able to observe somewhat
uncommon reactivity of the sulfoxide 26. First
of all, this compound, upon treatment with O-
mesitylsulfonylhydroxylamine gave, instead of the
expected optically active sulfoximine 28 (the product
of oxidation), the achiral sulfone 29 (Scheme 14).
The second reaction which shows unexpected
reactivity of the sulfoxide 26 is the HCl-catalyzed
SCHEME 8
SCHEME 10

Unexpected Conversions of Selected Heteroorganic Compounds 441
SCHEME 11
SCHEME 15
reduction by triphenylphosphine. It was found that
this reaction is completed at room temperature after
1 min whereas the reduction of diphenyl sulfoxide
under the same reaction conditions has a half-time
equal approximately to 26 h (Scheme 15).
UNEXPECTED REACTIONS OF
HYPERVALENT SULFUR AND
SELENIUM DERIVATIVES
SCHEME 12
Acid-catalyzed rearrangement of spirosulfurane
oxide 31, derived from the bidentate cumyl ligand of
the unsaturated sulfone 32, was reported by Martin
SCHEME 13
SCHEME 14
SCHEME 16

442 Drabowicz
In a sharp contrast to the sulfurane oxide 31,
the analogous selenurane oxide 34 does not un-
dergo such a rearrangement, even in the presence of
gaseous HCl. As a matter of fact, it is unexpectedly
reduced under these conditions to the parent selenu-
rane 35 (Scheme 17).
Also, in sharp contrast to the sulfurane oxide
31, which is opened upon treatment with Ph3P to
the unsaturated sulfone 32, the selenurane oxide 34
is converted by treatment with two equivalents of
Ph3P, and in the presence of water, into the symmet-
rical hydroxyalkyl selenide 37 with simultaneous ox-
idation of triphenylphosphine to the corresponding
oxide (Scheme 18). An independent experiment has
shown that the selenurane 38 is also converted to
the selenide 37 upon treatment with an equivalent
amount of Ph3P and water.
ACKNOWLEDGMENT
"
The author thanks Professors M. Mikolajczyk and
Y. Yamamoto for helpful discussions and Associate
Professor J. Omelan´czuk and Dr. P. Lyz˙wa for their
"
SCHEME 17
contribution to the chemistry of t-butylphenylphos-
phine oxide.
and Adzima [14]. We have found that this reaction
can be catalyzed by a few so-called soft nucleophiles,
but the speed of the conversion is very low (J.
Drabowicz, unpublished results) (Scheme 16).
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SCHEME 18