This article was downloaded by: [Purdue University]On: 12 March 2013, At: 15:49Publisher: Taylor & FrancisInforma Ltd Registered in England and Wales Registered Number: 1072954Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH,UK

Synthetic Communications: AnInternational Journal for RapidCommunication of SyntheticOrganic ChemistryPublication details, including instructions forauthors and subscription information:http://www.tandfonline.com/loi/lsyc20

Synthesis of 1,3-DioxanesCatalyzed by TsOH-SiO2 UnderSolvent-Free ConditionsKalyan Jyoti Borah a , Mridula Phukan a & Ruli Boraha

a Chemical Sciences Department, Tezpur University,Napaam, Assam, IndiaVersion of record first published: 09 Sep 2008.

To cite this article: Kalyan Jyoti Borah , Mridula Phukan & Ruli Borah (2008):Synthesis of 1,3-Dioxanes Catalyzed by TsOH-SiO2 Under Solvent-Free Conditions,Synthetic Communications: An International Journal for Rapid Communication ofSynthetic Organic Chemistry, 38:18, 3082-3087

To link to this article: http://dx.doi.org/10.1080/00397910802045618

PLEASE SCROLL DOWN FOR ARTICLE

Full terms and conditions of use: http://www.tandfonline.com/page/terms-and-conditions

This article may be used for research, teaching, and private study purposes.Any substantial or systematic reproduction, redistribution, reselling, loan,sub-licensing, systematic supply, or distribution in any form to anyone isexpressly forbidden.

The publisher does not give any warranty express or implied or make anyrepresentation that the contents will be complete or accurate or up todate. The accuracy of any instructions, formulae, and drug doses should beindependently verified with primary sources. The publisher shall not be liablefor any loss, actions, claims, proceedings, demand, or costs or damageswhatsoever or howsoever caused arising directly or indirectly in connectionwith or arising out of the use of this material.

Dow

nloa

ded

by [

Purd

ue U

nive

rsity

] at

15:

49 1

2 M

arch

201

3

Synthesis of 1,3-Dioxanes Catalyzed byTsOH-SiO2 Under Solvent-Free Conditions

Kalyan Jyoti Borah, Mridula Phukan, and Ruli BorahChemical Sciences Department, Tezpur University, Napaam, Assam, India

Abstract: Silica-supported p-toluene sulfonic acid is found to be an excellentcatalyst for the Prins reaction to produce 1,3-dioxanes in good yields from olefinsand aliphatic aldehydes in dichloromethane at room temperature and solventlessmicrowave irradiation within a short reaction time.

Keywords: Microwave, p-toluene sulfonic acid, prins reaction, solventless

INTRODUCTION

The acid-catalyzed condensation of olefins with carbonyl compounds isan important reaction for carbon–carbon bond formation,[1] which is wellknown as the Prins reaction (Scheme 1). This reaction is one of theefficient methods for the synthesis of 1,3-dioxanes in the presence of con-ventional Lewis or Brønsted acids using volatile organic solvents.

Reports on a large number of synthetic methods[1–3] involve high-temperature reaction conditions, prolonged reaction times (6–20 h), useof a stoichiometric amount of catalyst, environmental pollution fromorganic solvents, and complicated product purification. In recent years,the use of solid catalysts such as resin,[4] zeolite,[5] and K10 clay[2] havegained importance in the Prins[6] reaction because of their environmentalcompatibility, greater selectivity, experimental simplicity, low cost, andsimple purification of the products. Chandrasekhar and Reddy[7] firstreported the microwave-assisted Prins synthesis of 1,3-dioxane usingTaCl2-SiO2 as catalyst under solvent-free conditions. Generally, most

Received January 16, 2008.Address correspondence to Ruli Borah, Senior Lecture, Department of Chemi-

cal Sciences, Tezpur University, Napaam, Tezpur-784028 Assam, India. E-mail:ruli@tezu.ernet.in

Synthetic Communications1, 38: 3082–3087, 2008

Copyright # Taylor & Francis Group, LLC

ISSN: 0039-7911 print/1532-2432 online

DOI: 10.1080/00397910802045618

3082

Dow

nloa

ded

by [

Purd

ue U

nive

rsity

] at

15:

49 1

2 M

arch

201

3

of the conventional methods[8] include the use of paraformaldehyde as aformaldehyde source. The direct use of formalin solution is highly desir-able because it reduces the use of toxic and volatile organic solvents suchas acetonitrile, toluene, and dioxane to dissolve solid paraformaldehyde.Only a few[3] reports are available in literature regarding using formalinas a starting compound.

In this context, new methods and environmentally friendly con-ditions for the synthesis of 1,3-dioxane are still demand for their use ofsolventless conditions, greater selectivity, shorter reaction times, and sim-ple workup procedure.

RESULTS AND DISCUSSION

For comparative study, we investigated TsOH=TsOH-SiO2-catalyzedPrins reaction of paraformaldehyde (Tables 1 and 2) and various alkenesunder both solvent and solvent-free conditions. These studies revealedthat the Prins reactions of paraformaldehyde and substituted styreneselectively produced 1,3-dioxane in the presence of TsOH-SiO2 as catalystwithin 5 min (Table 2, entries 2, 5, 8, and 10) with microwave irradiation(180 W) as compared to reaction in dichloromethane (Table 1, entries 2,6, 8, and 10). In addition, p-toluene sulfonic acid–catalyzed Prins reac-tion of formalin and styrene derivatives (Table 2, entries 6, 9, and 11)showed excellent results under microwave irradiation. Interestingly, Duand Tian[3] reported that no 1,3-dioxane product was found for TsOH-catalyzed Prins reaction of formalin and styrene under reflux for 20 h.Similarly, in this case also, no reaction was observed for the Prins reac-tion of formalin and styrene in dichloromethane after 24 h (Table 1,entries 3 and 4), with stirring at room temperature using TsOH=TsOH-SiO2 as catalysts. The results in Table 1 indicate that in contrast to theconventional methods,[2,3,9] TsOH=TsOH-SiO2-catalyzed Prins reactionof different olefins and paraformaldehyde took less reaction time

Scheme 1. Microwave-assisted solvent-free Prins reaction.

Synthesis of 1,3-Dioxanes 3083

Dow

nloa

ded

by [

Purd

ue U

nive

rsity

] at

15:

49 1

2 M

arch

201

3

(30 min–3 h) in dichloromethane at room temperature. All other alde-hydes, such as pentanal and octanal, were similarly transformed to thecorresponding 1,3-dioxanes (Table 2, entries 14, 15, and 16) afterirradiation with styrene in microwaves for 2–3 min. Furthermore,the TsOH-SiO2-catalyzed Prins reaction yielded more product (Table 1,entries 2, 6, 8, and 10) as compared to TsOH-catalyzed reaction(Table 1, entries 1, 5, 7, and 9) in dichloromethane within a short period.Again, microwave irradiation decreases the selectivity of TsOH-catalyzedPrins reaction for the formation of 1,3-dioxane (Table 2, entry 1) deriva-tives. It was found that the alkyl-substituted olefins afforded the corre-sponding 1,3-dioxanes in low yields (Table 1, entries 12, 13, and Table2, entry 12) as compared to styrene derivatives.

EXPERIMENTAL

General

All chemicals are commercially available and were used withoutfurther purification. The products were characterized by 1H NMR,MS, and CHN analysis and also by comparison with literature[2,4,8,9]

data.

Table 1. Prins reaction in dichloromethane catalyzed by TsOH-SiO2

Entry Alkene AldehydeSolid support

(silica gel) Time Yield (%)a,b

1 Styrene HCHO — 1 h 752 Styrene HCHO 1g 30 min 823 Styrene Formalin — 24 h No reaction4 Styrene Formalin 1g 24 h No reaction5 a-Methyl styrene HCHO — 90 min 706 a-Methyl styrene HCHO 1g 30 min 857 p-Chloro-styrene HCHO — 3 h 858 p-Chloro-styrene HCHO 1g 2 h 899 p-Methoxy styrene HCHO — 90 min 78

10 p-Methoxy styrene HCHO 1 g 70 min 8611 1-Octene Formalin — 20 h No reaction12 1-Octene HCHO 1g 90 min 6713 1-Octene HCHO — 2 h 62

aAll products were characterized by 1H NMR, MS, and CHN analysis and alsoby their comparison with literature[2,4,8,9] data.

bIsolated yields.

3084 K. J. Borah, M. Phukan, and R. Borah

Dow

nloa

ded

by [

Purd

ue U

nive

rsity

] at

15:

49 1

2 M

arch

201

3

Typical Procedures for the Preparation of 1,3-Dioxanes

Microwave Method

A mixture of styrene (3 mmol), paraformaldehyde (3 mmol), and p-toluenesulfonic acid (0.5 mmol) was mixed thoroughly with activated silica gel(1 g, 60–120 mesh, dried overnight at 100 �C) at room temperature for15 min. The mixture was irradiated in a microwave oven (180 W) for5 min. After completion of the reaction as indicated by thin-layer chromato-graphy (TLC), the reaction mixture was cooled to room temperature. The

Table 2. Microwave-assisted Prins reaction catalyzed by TsOH-SiO2

Entry Alkene AldehydeMicrowavepower (W)

Solidsupport

(silica gel)Time(min) Yield (%)a,b

1 Styrene HCHO 180 — 5 Moreproducts

2 Styrene HCHO 180 1 g 5 853 Styrene Formalin 180 — 2 904 Styrene Formalin 180 1 g 2 No reaction5 a-Methyl

styreneHCHO 180 1 g 4 90

6 a-Methylstyrene

Formalin 180 — 2 85

7 a-Methylstyrene

Formalin 180 1 g 4 No reaction

8 p-Chloro-styrene

HCHO 180 1 g 5 95

9 p-Chloro-styrene

Formalin 180 — 3 96

10 p-Methoxystyrene

HCHO 180 1 g 4 94

11 p-Methoxystyrene

Formalin 180 — 2 92

12. 1-Octene HCHO 300 1 g 5 7013 1-Octene Formalin 300 — 5 No reaction14 Styrene Pentanal 180 1 g 1 7615 a-Methyl

styrenePentanal 180 1 g 2 72

16 Styrene Hexanal 300 1 g 7 52

aAll products were characterized by 1H NMR, MS, and CHN analysis and alsoby their comparison with literature [2,4,8,9] data.

bIsolated yields.

Synthesis of 1,3-Dioxanes 3085

Dow

nloa

ded

by [

Purd

ue U

nive

rsity

] at

15:

49 1

2 M

arch

201

3

resulting product was directly charged onto a small silica-gel column andeluted with a mixture of ethyl acetate–n-hexane (1:9) to find pure 1,3-diox-ane (85%).

Conventional Method

A mixture of styrene (3 mmol), paraformaldehyde (3 mmol), andp-toluene sulfonic acid (0.5 mmol) was stirred in dichloromethane(5 ml) at room temperature for 1 h. After completion of the reactionas indicated by TLC, the reaction mixture was diluted with water andextracted with ether (2� 10 ml). The combined organic layers were driedover anhydrous sodium sulfate and distilled under reduced pressure in arotary evaporator. The crude reaction mixture was further purified bycolumn chromatography using ethyl acetate–n-hexane (1:9) as eluentto find pure product 1,3-dioxane (75%).

Spectral Data of Selected Products

4-Phenyl-1,3-dioxane (entry 1, Table 1):

1H NMR (400 MHz, CdCl3) d 1.68–1.75 (1H, m), 2.04–2.17 (1H, m),3.83–3.93 (1H, m), 4.17–4.23 (1H, m), 4.65 (1H, d, J ¼ 11.2 Hz), 4.90(1H, d, J ¼ 6.4Hz), 5.20 (1H, d, J ¼ 6.4 Hz), 7.23–7.30 (5H, m); EIMSm=z 164 (Mþ), 118, 105 (100), 77. Found: C, 73; H, 7.61%. Calcd. forC10H12O2: C, 73.15; H, 7.37%. 13C NMR d 33.9, 66.9, 78.7, 94.2,125.7, 127.9, 128.5, 141.5.

4-methyl-4-phenyl-1,3-dioxane (entry 6, Table 1):

1H NMR (400 MHz, CdCl3) d1.45(3H, s) 2.9–2.18 (1H, m), 2.25–2.32(1H, m), 3.65–3.74 (1H, m), 3.90–3.96 (1H, m), 4.73 (1H, d, J ¼ 6.4Hz), 4.91 (1H, d, J ¼ 6.4Hz), 7.23–7.31 (5H, m); EIMS; m=z 178(Mþ), 163, 132, 117, 105 (100), 91, 77, 51. Found: C, 74.21; H, 7.98%.Calcd. for C11H14O2: C, 74.13; H, 7.92%. 13C NMR d 32.1, 34.9, 63.6,75.7, 89.1, 125.7, 1

CONCLUSIONS

This article describes an efficient method for the synthesis of 1,3-dioxanewith microwaves without using any organic solvent (using paraformalde-hyde as and formalin as starting compound) in good yields.

3086 K. J. Borah, M. Phukan, and R. Borah

Dow

nloa

ded

by [

Purd

ue U

nive

rsity

] at

15:

49 1

2 M

arch

201

3

ACKNOWLEDGMENTS

The authors are thankful to the Council of Scientific and IndustrialResearch, New Delhi, India, for awarding a research grant (No.01(2067)=06=EMR-II) to R. B.

REFERENCES

1. (a) Adams, D. R.; Bhatnagar, S. P. The Prins reaction. Synthesis 1977, 10, 661;(b) Arundale, E.; Mikeska, L. A. The olefin–aldehyde condensation–The Prinsreaction. Chem. Rev. 1952, 51, 505.

2. Tateiwa, J.; Hashimoto, K.; Yamauchi, T.; Uemura, S. Cation-exchangedmontmorillonite (Mnþ-Mont)–catalyzed Prins reaction. Bull. Chem. Soc.Jpn. 1996, 69, 2361.

3. Du, Y.; Tian, F. Efficient synthesis of 1,3-dioxanes catalyzed by trifluoro-methanesulfonic acid using formalin as formaldehyde source. Catal. Commun.2007, 8, 2012.

4. (a) Delmas, M.; Gaset, A. Selective synthesis of 4-aryl-1,3-dioxanes fromarylalkenes and paraformaldehyde using an ion exchange resin as catalyst:Extension to natural compounds. Synthesis 1980, 11, 871; (b) Gharbi, R. E.;Delmas, M.; Gaset, A. Condensation of substituted styrenes with aliphaticand aromatic aldehydes: An extension of the Prins reaction. Synthesis,1981, 5, 361.

5. Aramendia, M. A.; Borau, V.; Jimenez, C.; Marinas, J. M.; Romero, F. J.;Urbano, F. J. Catalytic use of zeolites in the Prins reaction of arylalkenes.Catal. Lett. 2001, 73, 203.

6. (a) Yadav, J. S.; Reddy, B. V. S.; Sekhar, K. C.; Gunasekar, D. Amberlyst-15-catalyzed novel synthesis of tetrahydropyranols. Synthesis 2001, 6, 885; (b)Yadav, J. S.; Reddy, B. V. S.; Kumar, G. M.; Murthy, C. V. S. R. Montmor-illonite clay catalyzed in situ Prins-type cyclisation reaction. Tetrahedron Lett.2001, 42, 89.

7. Chandrasekhar, S.; Reddy, B. V. S. First TaCl5-SiO2-catalyzed Prins reaction:Comparative study of conventional heating vs microwave irradiation. Synlett,1998, 8, 851.

8. Bach, T.; Lobel, J. Selective Prins reaction of styrenes and formaldehydecatalyzed by 2,6-di-tert-butylphenoxy(difluoro)borane. Synthesis 2002, 17, 2521.

9. Yadav, J. S.; Reddy, B. V. S.; Bhaishya, G. InBr3-[bmim]PF6: A novel andrecyclable catalytic system for the synthesis of 1,3-dioxane derivatives. GreenChem. 2003, 5, 264.

Synthesis of 1,3-Dioxanes 3087

Dow

nloa

ded

by [

Purd

ue U

nive

rsity

] at

15:

49 1

2 M

arch

201

3