250
Chemistry Letters 2002
Polymer-supported Sulfinimidoyl Chloride as a Useful Reagent for Oxidation of
Various Alcohols to the Corresponding Carbonyl Compounds
Jun-ichi Matsuo, Asahi Kawana, Khanitha Pudhom, and Teruaki MukaiyamaÃ
Department of Applied Chemistry, Faculty of Science, Science University of Tokyo, Kagurazaka, Shinjuku-ku, Tokyo 162-8601
(Received November 22, 2001; CL-011184)
Polymer-supported sulfinimidoyl chloride was prepared in
four steps from chloromethyl polystyrene resin. Stoichiometric
and catalytic oxidations of various alcohols to the corresponding
carbonyl compounds were carried out cleanly by using the
prepared polymer-bound oxidant.
polystyrene resin8 according to the reported procedure,9 and the
loading of the arylthiol group was determined by isolation of
triphenylmethane formed after deprotection of 4.7 The free thiol
group of thus prepared 5 was acetylated with acetyl chloride and
pyridine to give aryl thioacetate 6.7 The loading (0.43 mmol/g) of
the thioacetate group was determined by isolation of 0.43 mmol of
N-benzylacetamide after treating 1g of 6 with 1.8 mmol of
benzylamine in refluxing 1,2-dichloroethane for 6 h. The bright
yellow polymer-supported oxidizing agent 37 was obtained by the
reaction of 6 and N,N-dichloro-t-butylamine according to the
procedure for the preparation of 1,1a followed by washing the
resin with dry dichloromethane and drying it in vacuo at 60 ꢀC for
1h. The substantial loading (0.18 mmol/g) of the sulfinimidoyl
chloride group10 was determined by detecting p-methoxyben-
zylchloride (0.18 mmol) by GC-analysis after treating 3 (1g) with
p-methoxybenzylalcohol (0.5 mmol) in dichloromethane at room
temperature for 2 h. The polymer-supported oxidizing agent 3
was stable at room temperature in a sealed bottle under an inert
gas.11 Its oxidizing ability did not change after keeping 3 at room
temperature for eight days.
Stoichiometric oxidation of various primary and secondary
alcohols to the corresponding aldehydes and ketones was
performed by using 3 and ethyldiisopropylamine12 (Table 1).
Oxidation of benzylic and allylic alcohols proceeded smoothly at
À78 ꢀC within 30 min by adding the mixture of alcohol and
ethyldiisopropylamine to the oxidizing agent 3 (Table 1, entries
1–4, Method A). On the other hand, for the efficient oxidation of
aliphatic primary and secondary alcohols, it was necessary to add
ethyldiisopropylamine to the premixed slurry of alcohol and 3 at
À78 ꢀC (Table 1, entries 6–8, Method B). In the above oxidation
of using 3, undesirable co-products were not detected after the
reaction and it obviously simplified the work-up procedures.
Typical experimental procedure for the stoichiometric
oxidation of alcohol with 3 is as follows (Table 1, entry 1): to a
slurry of 3 (0.18 mmol/g, 1.0 g, 0.18 mmol) in CH2Cl2 (10 mL)
Since N-t-butylbenzenesulfinimidoyl chloride (1) was first
introduced as an effective oxidizing agent for alcohols to carbonyl
compounds,1 it has been found to be useful also in other oxidation
reactions: for example, oxidation of amines to imines,2 oxidation
of hydroxylamines to nitrones,3 and one-pot dehydrogenation of
saturated ketones to ꢀ,ꢁ-unsaturated ones.4 However, N-t-
butylbenzenesulfenamide (2), a reduced form of 1, had to be
separated by column chromatography after the above-mentioned
oxidation reactions of using more than stoichiometric amounts of
1. Therefore, two approaches were considered to improve the
troublesome work-up procedures: one was a development of
catalytic oxidation of alcohols by using a catalytic amount of
sulfenamide 2, and the other was that of a polymer-supported
sulfinimidoyl chloride. Recently, the former was established by
using N-chlorosuccinimide (NCS) as a co-oxidant in the presence
of potassium carbonate.5 In this communication, we would like to
describe on the latter subject which consisted of i) preparation of
polymer-supported sulfinimidoyl chloride 3, ii) stoichiometric
oxidation of various alcohols by using 3, and iii) 3-catalyzed
oxidation of alcohols with N-chlorosuccinimide.
Scheme 1 shows preparation of polymer-supported oxidizing
agent6 3 which has the sulfinimidoyl chloride group at its termini.
Polymer-supported arylthiol 57 was prepared from chloromethyl
was added
a mixture of p-nitrobenzylalcohol (15.3 mg,
0.10 mmol) and ethyldiisopropylamine (25.8 mg, 0.20 mmol) in
CH2Cl2 (2 mL) at À78 ꢀC. The reaction mixture was stirred at
À78 ꢀC for 30 min, and the reaction was quenched by adding H2O
(2 mL). The mixture was filtered through Celite pad, and filtrate
was extracted with CH2Cl2. The combined organic extracts were
washed with H2O and brine, dried over anhydrous Na2SO4,
filtered and concentrated. The crude product was purified by
preparative TLC to afford p-nitrobenzaldehyde (14.8 mg, 98%).
Two successive synthetic reactions composed of alcohol-
oxidation and carbon-carbon bond formation, which were often
operated in organic synthesis, were efficiently carried out by the
3-mediated oxidation because an oxidation product was obtained
just by filtering the reaction mixture. Indeed, oxidation of p-
nitrobenzylalcohol and BF3-catalyzed aldol reaction of thus
Scheme 1.
Copyright Ó 2002 The Chemical Society of Japan