InCl3 as an efficient catalyst for cyclotrimerization of aldehydes: Synthesis of 1,3,5-Trioxane under solvent-free conditions

Article abstract of DOI:10.1080/00397910500290524

1,3,5-Trioxanes derived from aldehydes were synthesized using indium trichloride as a catalyst. Cyclotrimerization of the aldehydes gave excellent yields under neat conditions within a short span of time. Copyright Taylor & Francis, Inc.

Full text of DOI:10.1080/00397910500290524

Synthetic Communicationsw, 35: 2801–2804, 2005
Copyright # Taylor & Francis, Inc.
ISSN 0039-7911 print/1532-2432 online
DOI: 10.1080/00397910500290524
InCl3 as an Efficient Catalyst for
Cyclotrimerization of Aldehydes: Synthesis
of 1,3,5-Trioxane Under Solvent-Free
Conditions
E. Elamparuthi, E. Ramesh, and R. Raghunathan
Department of Organic Chemistry, University of Madras, Chennai, India
Abstract: 1,3,5-Trioxanes derived from aldehydes were synthesized using indium
trichloride as a catalyst. Cyclotrimerization of the aldehydes gave excellent yields
under neat conditions within a short span of time.
Keywords: Aldehyde, cyclotrimerization, InCl3, solvent-free, trioxane
INTRODUCTION
1,3,5-Trioxanes have substantial application as flavoring materials;[1] carriers
for scents, repellents, and deodorants;[2] insecticides,[3] constituents of a
stabilizing solution in color photography; burning regulators in fumigants
for potato tuber sprouting inhibition; and the basis for many polymers and
copolymers.[4,5] In general, they are formed by cyclotrimerization of
aldehydes catalyzed by heteropolyacids,[6] Lewis acids such as zinc
chloride,[7] tantalum pentachloride,[8] and other catalysts investigated
including zeolites,[9] methylrheniumtrioxide,[10] acetyltriphenylphospho-
[13]
niumbromide,[11] trimethylsilyl chloride,[12] and H3PW12O40 xH2O.
.
The utility of InCl3 is a reagent of choice for many transformations.[14]
Here we report yet another application of InCl3 for trimerization of
aldehydes (Scheme 1).
Received in India May 30, 2005
Address correspondence to R. Raghunathan, Department of Organic Chemistry,
University of Madras, Guindy Campus, Chennai 600 025, India. Fax: 91-44-
22352494; E-mail: ragharaghunathan@yahoo.com
2801

2802
E. Elamparuthi, E. Ramesh, and R. Raghunathan
Scheme 1.
A mixture of isobutrylaldehye and 5 mol% of In(III) chloride for 2 min
gave a solid product, which upon recrystalization gave 1,3,5-trioxane (2).
1
The H NMR spectrum of (2) showed a CH proton appearing at 4.5 ppm.
The 13C NMR spectrum revealed characteristic carbon resonance at
110 ppm. GC-MS and elemental analysis supported the assigned structure.
To reveal the versatility of InCl3, many aldehydes were trimerized (Table 1).
Table 1. 1,3,5-Trioxane synthesis by InCl3 under solvent-free conditions at room
temperature
Entry
Aldehyde
Time (min)
Yield (%)a,b
1
2
3
4
5
6
Me2CHCHO
Me3CCHO
2
5
3
7
4
6
86
90
79
92
78
85
Ph(CH2)2CHO
MeCH2CHO
MeCHO
Me(CH2)2CHO
7
8
86
8
9
6
4
78
87
10
7
82
11
12
5
6
84
79
13
20
81
aAll the products were characterized by IR,1H,13C NMR, and mass spectroscopy and
by comparison with reported data.[8]
bYield is based on recrystalization.

Cyclotrimerization of Aldehydes
2803
Scheme 2.
The InCl3-catalyzed trioxane formation was attributed to the effective
coordination of the catalyst with carbonyl oxygen of aldehyde to form I. Con-
sequently the nucleophilic attack of second molecule of aldehyde to formed II,
which combines with another aldehyde molecule and concomitantly cyclized
to form 2 (Scheme 2).
In conclusion, InCl3 was found to be an efficient reagent for the cyclotri-
merization of aldehydes.
GENERAL EXPERIMENTAL PROCEDURE
A mixture of aldehyde (1 mmol) and InCl3 (5 mol %) was stirred under neat
conditions at rt (Table 1). The reaction was monitored by TLC and the
mixture was quenched with cold water and extracted with ether. The
organic layer was washed with brine and dried over Na2SO4. The solvent
was evaporated and the crude product was recrystallized (yield 78–92%).
2,4,6-Tris(2,6-dimethyl-hept-5-enyl)-1,3,5-trioxane. Viscous liquid; 1H
NMR (CDCl3, 500 MHz) d 0.80 (d, J ¼ 10 Hz, 9H), 1.28–1.31 (m, 6H),
1.51–1.54 (m, 6H), 1.55 (s, 9H), 1.63 (s, 9H), 1.63–1.67 (m, 3H), 1.72–
2.01 (m, 6H), 4.82 (t, J ¼ 5.35 Hz, 3H, –OCHO), 5.05 (t, J ¼ 6.75 Hz, 3H)
13C NMR (CDCl3, 125 MHz) d 25.4, 25.6, 27.7, 36.9, 50.9, 102.1, 126.0,
133.2, IR (KBr) 3068, 1642, 1443, 1354 cm21; MS m/z (relative intensity):
462.9 (Mþ, 4), 71.1 (100), 137 (77), 109.17 (50.2), 153 (36.6). Anal. calcd.
for C30H54O3: C, 77.80; H, 11.67. Found: C, 77.87; H, 11.65.
1
Triisopropyl-1,3,5-trioxane. White solid, mp 59–618C; H NMR (CDCl3,
500 MHz) d 0.94 (d, J ¼ 6.8 Hz, 18H, –CH3), 1.83–1.88 (m, 3H), 4.50
(d, J ¼ 5.5 Hz, 3H, –OCHO); 13C NMR (CDCl3, 125 MHz) d 16.7, 32.4,

2804
E. Elamparuthi, E. Ramesh, and R. Raghunathan
104.7; IR (KBr) 2958, 1470, 1355, 1263 cm21; MS m/z (relative intensity):
216 (Mþ, 1), 199 (94), 127 (100), 98 (55), 81 (83). Anal. calcd. for
C12H24O3: C, 66.63; H, 11.18. Found: C, 66.59; H, 11.14.
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