Preparation of 1,1′-oxy-bis(3,3-bis(trifluoromethyl)-3(1H)-1,2- benziodoxole) and 2-(N-(p-toluenesulfonyl)imino)iodobenzylmethyl ether

Article abstract of DOI:10.1080/00397910802474990

Conditions for improved preparation of the crystalline iodine(III) reagents [1,2-C6H4(C(CF3)2OI)]2O and 1,2-C6H4(CH2OMe)(I=NTs) are presented together with their x-ray structures. The former is prepared by hydrolysis of 1,2-C6H4(C(CF3)2OICl (x-ray) and allows the preparation of cyclic sulfates from alkenes; the latter fashions sulfamidate under related conditions. Copyright Taylor & Francis Group, LLC.

Full text of DOI:10.1080/00397910802474990

Synthetic Communications1, 39: 1065–1075, 2009
Copyright # Taylor & Francis Group, LLC
ISSN: 0039-7911 print=1532-2432 online
DOI: 10.1080/00397910802474990
Preparation of 1,10-Oxy-bis(3,3-bis
(trifluoromethyl)-3(1H)-1,2-benziodoxole) and
2-(N-(p-Toluenesulfonyl)imino)iodobenzylmethyl
Ether
Alexander J. Blake, Andrew Novak, Madeline Davies,
Richard I. Robinson, and Simon Woodward
School of Chemistry, University of Nottingham, Nottingham,
United Kingdom
Abstract: Conditions for improved preparation of the crystalline iodine(III)
reagents [1,2-C6H4(C(CF3)2OI)]2O and 1,2-C6H4(CH2OMe)(I¼NTs) are pre-
sented together with their x-ray structures. The former is prepared by hydrolysis
of 1,2-C6H4(C(CF3)2OICl (x-ray) and allows the preparation of cyclic sulfates
from alkenes; the latter fashions sulfamidate under related conditions.
Keywords: Alkene functionalization, hypervalent iodine reagents, nitrene
precursor, x-ray
INTRODUCTION
Hypervalent iodine species have become cornerstone oxidants in organic
synthesis.[1] In routine transformations, Dess–Martin periodane 1,[2]
iodosylbenzene 2,[3] and nitrene precursor 3[4] (Scheme 1) normally
deliver the expected alcohol dehydrogenation or catalytic epoxidation=
aziridination products in good yields. Highly reliable experimental condi-
tions have been described for the preparation of 1–3, and the former is
also commercially available. However, when more esoteric IIII or IV
Received August 28, 2008.
Address correspondence to Simon Woodward, School of Chemistry, Univer-
sity of Nottingham, University Park, Nottingham NG7 2RD, United Kingdom.
E-mail: simon.woodward@nottingham.ac.uk
1065

1066
A. J. Blake et al.
Scheme 1. Common (1–3) and poorly described (4 and 5) hypervalent iodine
reagents.
reagents are called upon to optimize a given synthetic transformation,
then optimal preparative procedures for these are not always available
in the primary literature. For example, only scant elements of the syn-
thetic sequences leading to 4 and 5 have made fleeting appearances,
and no detailed robust experimental procedures are available.[5,6] In this
note, we give optimized preparations of these compounds together with
some applications that we needed in a separate project.
RESULTS AND DISCUSSION
Dimeric 4 is prepared by the synthetic sequence shown in Scheme 2.
Chloro species 6 is an excellent precursor, but it has not been fully
described in the literature.[5] Crystallization of as colorless tablets allows
its facile purification and x-ray analysis, which clearly shows the T
geometry of the hypervalent iodine centre (Fig. 1a). The oxophilicity
of the I(III) center is evident from the comparison of the lengths of
˚
˚
the I–Cl (2.448 A) and I–O (2.109 A) bonds (Fig. 1a). The bromo analog
of 6 has been recently been used by Braddock in the bromination of
alkenes and adopts a similar geometry.[7] Hydrolysis of the I–Cl bond
in 5 was possible in a biphasic system using potassium hydride (KOH)
and a phase-transfer catalyst (PTC) (Scheme 2). Monitoring of the reac-
tion by thin-layer chromotography (TLC) showed the formation of two
new compounds of differing Rf value. Isolation of both compounds by

New Hypervalent Iodine Reagents
1067
Scheme 2. Preparation of 1,10-oxy-bis(3,3-bis(trifluoromethyl)-3(1H)-1,2-
benziodoxole) (4).
silica-gel column chromatography gave acceptable yields of the desired
dimer 4, along with known 7.[8] The former could be crystallized as color-
less blocks (Fig. 1b), again greatly facilitating its purification.
Although it is very popular as a nitrene source, compound 3 shows a
couple of negative features: first, its polymeric structure renders it highly
insoluble, and second, it is rather susceptible to hydrolysis reactions lead-
ing to its degradation to iodosylbenzene 2. In our use of 3, this proved a
major problem, and we speculated that an ortho-chelated version of 3
would be more resistant to hydrolysis events. We prepared 5 by the
chemistry of Scheme 3. Diacetate 9 has been mentioned in passing in
Figure 1. (a) Molecular structure of 6, left-hand side. Selected bond distances and
˚
angles: I–C(1) 2.108 (2), I–O 2.109 (6), I–Cl 2.448 (14) A; Cl–I–O 171.63 (4), C(1)–
I–Cl 92.60 (6), C(1)–I–O 79.24 (7)ꢀ. (b) Molecular structure of 4, right-hand side.
Selected bond distances and angles: I(1)–O(2) 2.0296 (15), I(1)–C(1) 2.097 (2),
I(1)–O(1) 2.1548 (15), O(2)–I (1A) 2.0300 (15), I(1A)–C(1A) 2.105 (2), I(1Aꢀ)-
˚
O(1A), 2.1407 (16) A; O(2)–I(1)–O(1) 167.72 (6), O(2)–I(1A)–O(1A) 168.00 (6) .

1068
A. J. Blake et al.
Scheme 3. Preparation of 12-(N-(p-toluenesulfonyl)imino)iodobenzylmethyl
ether (5).
the literature, but no experimental details or physical data were given.[6]
In our experience, formation of 9 is solvent sensitive—use of neat 37%
peracetic acid gave the best results, but the presence of a CH2Cl2 cosol-
vent led to lower yields (41–56%), mainly due to overoxidation at the
benzylic CH2 position, affording 2-iodobenzoic acid. When carrying
out the neat AcOOH oxidation on a larger scale, longer times were
required to ensure efficient contact mixing of all the reaction compo-
nents. For example, reaction at a 4-mmol scale took 45 min, whereas that
at 6 mmol took 60 min using the same 6:AcOOH ratio (1:2 equivalents).
However, in all cases, a high yield of 9 was realized on completion of the
reaction. Rewardingly, the new nitrene source 5 was appreciably soluble
and crystallised on slow evaporation of methanol solutions (Fig. 2).
Additionally, compound 5 was found to be thermally stable and rela-
tively nonhygroscopic. Exposure of 5 to atmopheric moisture for 2 days
left the compound unchanged, while stirring it in a biphasic CH2Cl2=H2O
system for 24 h resulted in the recovery of 5 in 75% yield.
Reagents 2–5 have been compared in the direct oxidative functionali-
zation of alkenes in the presence of SO3 ꢁ DMF.[9] Two alkenes were used in
this brief comparison (Table 1). Use of the bis compound 4 allowed high
yields of cyclic sulfate to be attained. Additionally, the greater hydrolytic
resistance of 5 allowed a significant increase in the sulfamidate yield.
Unfortunately, the highly Lewis acidic conditions of these reactions still
allowed N=O-exchange to a significant degree, leading to a significant
contamination by 12. Interestingly, the sulfamidates are isolated as single
regio isomers, which are assigned on the basis of nuclear Overhauser effect
(NOE) analysis of compound 11 as summarized in Scheme 4.

New Hypervalent Iodine Reagents
1069
Figure 2. Selected bond distances and angles for (5): C(8)–I(1) 2.13, O(3)–I(1)
ꢀ
˚
2.65 A; N(1)–I(1)–C(8) 98.48 . Data averaged from two independent molecules.
Table 1. Formation of cyclic sulfates and sulamidates using
reagents 2–5
Cyclic sulfate
yield (%)
Cyclic sulfamidate
yield (%)
Reagent
R
X
2
3
4
5
Et
Et
Ph
Ph
O
NTs
O
75
50
94
41
—
15
—
23
NTs

1070
A. J. Blake et al.
Scheme 4. NOE studies confirming structure of 11.
EXPERIMENTAL
General
Chromatography was performed using Fluorochem (35–70 micron) silica
gel and TLC analysis using Merck Kieselgel 60 F245þ366. Spectroscopic
instrumentation used has been described before.[10] Dimethylformamide
(DMF) was dried over activated 4A molecular sieves. Methanol was dis-
tilled from Mg(OMe)2. Hygroscopic SO3 ꢁ DMF was stored under argon.
The purity of AcOOH and hypervalent iodine reagents was confirmed by
iodometric titration.[11] Compound 6 was prepared by a literature proce-
dure.[5] Only limited data have appeared for compound 6; in our case, it
was purified by recrystallization from CH2Cl2 to give the title compound
as colorless tablets (Found: C, 26.98; H, 0.75%. Calc. for C9H4OIClF6: C,
26.73; H, 1.00%). Mp 170–173 ꢀC; lit.[5] 166–168 ꢀC; 1H NMR (270 MHz,
CDCl3) dH 8.09 (1H, d, J 8.3, Ar), 7.88–7.81 (1H, m, Ar), 7.74–7.72 (2H,
m, Ar); 13C NMR (68 MHz, CDCl3) dC 139.4, 133.9, 132.1, 131.7, 129.8
2
1
(septet, JCF 3), 128.6, 122.9 (q, JCF 290), 113.5; 19F NMR (282 MHz,
CDCl3) dF – 75.8; IR tmax (solid)=cmꢂ1 1270 w, 1195 m, 1103 w, 969 w,
728 w, 645 s; CIMS m=z 406 (MHþ, 37Cl, 32%), 404 (MHþ, 35Cl, 100);
HRMS: found (CI) MHþ 404.8964; C9H5OI35ClF6 requires M 404.8978;
Rf 0.59 (30% EtOAc in hexane).
1,10-Oxy-bis(3,3-bis(trifluoromethyl)-3(1H)-1,2-benziodoxole) 4
In a round-bottomed flask, 21 (0.50 g; 1.2 mmol), was dissolved in CH2Cl2
(10 mL), and a solution of KOH (77 mg; 1.4 mmol) in water (1.3 mL)
was added with stirring. Benzyltrimethylammonium chloride (20 mg;
0.07 mmol) was added as a PTC. After 15 min at rt, the CH2Cl2 layer
decolorized, and stirring was continued for a further 2 h. The organic layer
was separated and dried with MgSO4, and the solvent was removed to give
a white solid (0.46 g; 97%). Purification by column chromatography
(silica; 30% EtOAc in hexane as eluent) gave a white powder that was

New Hypervalent Iodine Reagents
1071
recrystallized from CH2Cl2 to give the title compound as colorless blocks
(163 mg; 34%). Found: C, 28.51; H, 1.12%; calc. for C18H18O3I2F12:C,
1
28.67; H, 1.07%. Mp 240–241 ꢀC; H NMR (100 MHz, DMSO-d) dH
7.99–7.92 (4H, m, Ar), 7.80–7.70 (4H, m, Ar); 13C NMR (68 MHz,
1
DMSO-d) dC 133.9, 133.4, 131.6, 131.4, 129.5 (m), 128.6, 124.0 (q, JCF
290), 117.8; 19F NMR (282 MHz, DMSO-d) dF – 75.8; IR tmax
(solid)=cmꢂ1 1261 m, 1185 s, 1142 m, 1130 m, 952 m, 730 m, 646 s; FABMS
m=z 755 (MHþ, 4%), 685 (100), 385 (55), 369 (35), 316 (63), 300 (39), 231
(75); HRMS: found (FAB) Mþ 753.8400. C18H8O3I2F12 requires M
753.8371; Rf 0.45 (30% EtOAc in hexane). Further elution afforded 1-
hydroxy-3,3-bis(trifluoromethyl)-3(1H)-1,2-benziodoxole[8] 7 as a white
solid (270 mg; 57%). Found: C, 28.25; H, 1.18%; calc. for C9H5O2IF6:C,
1
28.00; H, 1.31%. Mp 242–246 ꢀC; H NMR (270 MHz, DMSO-d6) dH
7.93–7.85 (2H, m, Ar), 7.74–7.65 (2H, m, Ar), 7.30 (1H, br s, OH inter-
changeable with D2O); FABMS m=z 387 (MHþ, 20%), 369 (14), 307
(19), 176 (28), 154 (100), 136 (84); Rf 0.15 (30% EtOAc in hexane).
Preparation of 2-(N-(p-Toluenesulfonyl)imino)iodobenzylmethyl Ether 5
1,2-Iodobenzylmethyl Ether 8
Commercial 2-iodobenzyl alcohol (10.00 g, 42.7 mmol) was treated with
sodium hydride (60% by weight in oil) (6.84 g, 170.9 mmol) in dry
DMF (215 mL) at ambient temperature (1 h). The creamy reaction mass
was treated with methyl iodide (11.2 mL, 179.3 mmol) and stirred at room
temperature (4 h). The reaction was quenched with water, and the pro-
duct was extracted into diethyl ether. Drying (MgSO4) and distillation
gave (7.93 g, 72%). Bp 239–240 ꢀC. 1H NMR (270 MHz, CDCl3) dH
7.83–6.94 (4H, m, Ar), 4.46 (2H, s, CH2OMe), 3.48 (3H, s, OMe); 13C
NMR (400 MHz, CDCl3) dC 138.6, 137.4, 127.4, 126.6, 126.0, 124.0,
76.6, 56.8; Rf 0.51 (10% diethyl ether in petrol).
2-(Bis-acetoxyiodo)-benzylmethyl Ether 9
Peracetic acid (37% by weight in AcOH, 50% activity) (6.63 g,
16.12 mmol) was added slowly to stirred 1,2-iodobenzylmethylether
(2.00 g, 8.06 mmol) over 30 min at 30 ꢀC. Effervescence was observed.
The reaction was complete after 1 h by TLC. The reaction was chilled
(ꢃ 0 ꢀC), and water (30 mL) was added, forming a yellow solution. The
product was extracted with chloroform (3 ꢄ 35 mL), and the combined
organic layers was washed with water and dried (MgSO4). The solvent
was removed, yielding the title product as a white solid (2.29 g, 78%).

1072
A. J. Blake et al.
1
Mp 87–89 ꢀC; H NMR (270 MHz, CDCl3) dH 8.20 (1H, d, J ¼ 7.9, Ar),
7.70–7.34 (3H, m, Ar), 4.73 (2H, s, CH2OMe) 3.47 (3H, s, OMe), 1.98
(6H, s, C(O)Me); 13C NMR (400 MHz, CDCl3) dC 176.5, 139.5, 137.3,
132.6, 130.2, 129.6, 123.9, 76.7, 58.7, 20.3; IR nmax (CHCl3 solution)=
cmꢂ1 2933 m, 1713 s, 1647 s, 1365 s, 1275 s, 1046 m; Rf 0.04 (10% diethyl
ether in petrol). Compound 9 has appeared in the literature,[6] but no data
were presented.
2-(N-(p-toluenesulfonyl)imino)iodobenzylmethyl Ether 5
To a stirred solution of KOH (2.07 g; 37.57 mmol) in anhydrous MeOH
(60 mL) under an inert atmosphere, p-toluenesulfonamide (2.57 g;
15.03 mmol) was added, and the solution was stirred for 30 min at rt.
The reaction mixture was cooled to 0 ꢀC, and 24 (5.50 g, 15.03 mmol)
was added and left at 5 ꢀC for 16 h. The resultant suspension was allowed
to settle, and solvent was removed by filter canula. Recrystallization from
anhydrous MeOH gave the title compound as a white powder (3.18 g;
1
51%). Mp 100–101 ꢀC; H NMR (270 MHz, CDCl3) dH 7.96–7.94 (1H,
m, Ar), 7.84–7.81 (2H, m, Ar), 7.39–7.15 (5H, m, Ar), 4.64 (2H, s,
CH2OMe), 3.47 (3H, s, OMe), 2.35 (3H, s, ArMe); 13C NMR (68 MHz,
CDCl3) dC 141.5, 140.8, 135.5, 130.8, 130.1, 129.1, 128.6, 127.9, 126.7,
113.0, 74.3, 58.6, 21.4; IR tmax (CHCl3 solution)=cmꢂ1 2960 w, 1566 w,
1454 w, 1128 w, 1135 s, 1082 s, 874 m.
General Procedure for the Direct Formation of Cyclic Sulfates and
Sulfamidates from Olefins, Using Hypervalent Iodine Reagents
To a flame-dried Schlenk tube under an inert atmosphere, the hyper-
valent iodine compound (0.5 mmol) and anhydrous CH2Cl2 (2 mL) were
added. The reaction mixture was stirred vigorously for 5 min until a free-
flowing suspension was observed. The addition of SO3 ꢁ DMF (76 mg;
0.5 mmol) produced a yellow gum after 10 min at rt. The reaction mixture
was cooled to 0 ꢀC and alkene (0.5 mmol) added, after which time the
solution was allowed to warm to rt and completion was determined by
TLC analysis. Concentration of the reaction mixture in vacuo and puri-
fication by flash chromatography (silica; CH2Cl2 in hexanes as eluent)
gave the pure cyclic sulfate or sulfamidate product.
Hexane-1,2-diol Cyclic Sulfate 10
Purification by filtration chromatography (over silica gel ꢃ1 g; 25%
CH2Cl2=light petrol) to remove iodobenzene, then flushing with CH2Cl2,

New Hypervalent Iodine Reagents
1073
gave 10 (68 mg, 75%) as a colorless oil. Rf 0.65 (CH2Cl2). dH (400 MHz,
CDCl3): 5.02–4.95 (m, 1H; CHO); 4.71 (dd, 1H, J ¼ 9.0, 6.0; CH2aO);
4.34 (apparent t, 1H, J ¼ 6.0; CH2bO); 1.96–1.91 (m, 1H; CH2aCHO);
1.83–1.75 (m, 1H; CH2bCHO); 1.53–1.31 (m, 4H; chain-CH2); 0.94
(t, 3H, J ¼ 6.7; Me). dc (100 MHz, CDCl3): 83.0 (CH), 72.9 (CH2),
32.0, 26.7, 22.2, 13.8 (CH3). These data are in agreement with literature
values.[12]
5-Butyl-3-[(4-tolyl)sulfonyl]-1,2,3-oxathiazolidine 2,2-dioxide 11
Compound 11 was prepared from PhI¼NTs (1.12 g, 3.0 mmol) in anhy-
drous dichloromethane (10 mL) using SO3 ꢁ DMF (460 mg, 3.0 mmol)
and 1-hexene (0.31 mL, 2.5 mmol). Purification by flash chromatography
(CH2Cl2) gave 11 (122 mg, 15%), which was isolated as a white solid;
1
mp > 175 ꢀC (dec.). H NMR (270 MHz, CDCl3) dH 7.93 (2H, dd, J 8.0
and 1.0, Ar), 7.41 (2H, dd, J 8.0 1.0, Ar), 4.76–4.71 (1H, m, CHN),
3.97 (1H, dd, J 9.3 5.7, CH2aO), 3.53 (1H, apparent t, J 9.1, CH2bO),
2.48 (3H, s, Me), 1.85–1.77 (1H, m, CH), 1.67–1.60 (1H, m, CH), 1.43–
1.26 (6H, m, 3CH2), 0.89 (3H, t, J 8.0, Me); 13C NMR (100 MHz, CDCl3)
dC 146.2, 133.0, 130.2, 128.8, 80.1, 52.1, 32.1, 26.6, 22.1, 21.8, 13.7. nmax
(solid state)=cmꢂ1: 1373 vs, 1202 s, 1169 vs, 1090 m, 1014 w, 937 m, 850 m,
815 m, 709 m, 694 m; HRMS [found (EIþ) Mþ 333.0714; C13H19NO5S2
requires 333.0705]. Rf 0.72 (CH2Cl2).
4-Phenylbutane-1,2-diol Cyclic Sulfate 12
Preparation according to the general procedure using PhI¼O and
1
4-phenyl butane (0.5 mmol) gave 12 as a colorless oil (85 mg; 75%). H
NMR (270 MHz, CDCl3) dH 7.36–7.18 (5H, m, Ar) 4.99–4.89 (1H, m,
CHO), 4.63 (1H, dd, J 9.5 6.7, CH2aO), 4.30 (1H, dd, J 9.5 9.0, CH2bO),
2.93–2.85 (1H, m, CH2aCHO), 2.81–2.70 (1H, m, CH2bCHO), 2.37–2.25
(1H, m, PhCH2a), 2.10–1.97 (1H, m, PhCH2b); 13C NMR (100 MHz,
CDCl3) dC 139.1, 128.8, 128.4, 126.8, 81.8, 72.6, 33.9, 33.8; IR tmax
(CHCl3 solution)=cmꢂ1 3030 m, 2955 m, 1702 w, 1603 w, 1497 w, 1407 s,
1205 s, 1032 s, 822 m; HRMS: found (ES) MNaþ 251.0347; C10H12O4SNa
requires M 251.0354; Rf 0.31 (50% CH2Cl2 in hexane). These data are
concordant with literature values.[13]
5-(3-Phenylproyl)-3-[(4-tolyl)sulfonyl]-1,2,3-oxathiazolidine 2,2-Dioxide 13
Preparation according to general procedure using 5 and 4-phenylbutene
(0.5 mmol) gave 13 as a colorless powder (37 mg; 23%); mp 130–132 ꢀC;

1074
A. J. Blake et al.
1H NMR (400 MHz, CDCl3) dH 7.90 (2H, d, J 8.4, Ar), 7.38 (2H, d, J 8.4,
Ar), 7.32–7.13 (3H, m, Ar), 7.11 (2H, d, J 8.2, Ar), 4.72–4.66 (1H, m,
CHO), 3.91 (1H, dd, J 9.3 5.7, CH2aNTs), 3.53 (1H, apparent t, J 8.7,
CH2bNTs), 2.82–2.75 (1H, m, CH2aCHO), 2.70–2.63 (1H, m,
CH2bCHO), 2.47 (3H, s, ArMe), 2.19–2.10 (1H, m, PhCH2a), 1.97–1.88
(1H, m, 1H; PhCH2b); 13C NMR (100 MHz, CDCl3) dC 146.5, 139.3,
130.4, 129.1, 129.0, 128.9, 128.6, 127.0, 79.4, 52.2, 34.4, 31.0, 22.1; IR
tmax solid=cmꢂ1 1592 w, 1493 w, 1453 w, 1370 s, 1203 m, 1167 m,
þ
1091 w, 1007 w, 929 m, 900 w, 814 s; EIMS m=z 278 (M-PhCH2CH2
,
12%), 226 (11), 91 (100) molecular ion not observed; Rf 0.13 (50%
CH2Cl2 in hexane).
Crystallographic Data
X-ray data for compounds 6, 4, and 5 are available from the Cambridge
Crystallographic Database, citing CCDC-633375, CCDC-633375, and
CCDC 699416, respectively. These data can be obtained free of charge
via www.ccdc.cam.ac.uk/data_request/cif.
ACKNOWLEDGMENTS
Financial support from the European Union (EU) associated with
the Ligbank1 project (FP6-NMP3-C-2003-505267) and the COST
(European Cooperation in the field of Scientific and Technical Research)
program is acknowledged. One of us (A. N.) is grateful to GlaxoSmithK-
line for the provision of a studentship.
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