Rhodium complex encapsulated functionalized hexagonal mesoporous silica for heterogeneous hydroaminomethylation

doi:10.1016/j.apcata.2012.12.021

Applied Catalysis A: General

Volume 453, 26 February 2013, Pages 159-166

https://doi.org/10.1016/j.apcata.2012.12.021 Get rights and content

Abstract

HRh(CO)(PPh₃)₃ complex was encapsulated into the pores of amino functionalized hexagonal mesoporous silica. The catalyst was characterized by physico-chemical techniques like P-XRD, ³¹P-CPMAS NMR, FT-IR, SEM, ICP and N₂ adsorption analysis. The catalyst was active for hydroaminomethylation and a variety of alkenes and amines were used as reactants for hydroaminomethylation. The catalyst afforded to achieve 100% conversion with high (>95%) selectivity to corresponding amines. Parametric variations were performed by taking 1-hexene and morpholine as representative reactants for the study of catalyst amount, temperature, pressure and 1-hexene:morpholine ratio. Significant amounts of aldehydes and enamines were observed during the course of the reaction indicating that there could be two possible rate determining steps. The catalyst was effectively recycled up to five times without much loss in its activity and selectivity.

Graphical abstract

Highlights

► HRh(CO)(PPh₃)₃ encapsulated in functionalized HMS. ► Hydroaminomethylation with high conversion and selectivity to amine. ► Recyclable upto five times without loss in activity.

Introduction

Aliphatic amines are one of the very important classes of compounds used in bulk as well as fine chemicals in the chemical and pharmaceutical industry [1], [2]. Around one million tons of amines are produced annually for different uses. General methods for amine synthesis include hydrocyanation of olefins followed by reduction, reductive amination of carbonyl compounds and alkylation of organic halides with ammonia. These methods generally have drawbacks of expensive starting materials, formation of byproducts and the need of protecting and deprotecting steps involved during the synthesis. From both economic and environmental points of view, developing new versatile and direct single pot synthesis routes to amines from inexpensive and easily available feedstock is most desirable. Hydroamination [3], [4], [5] and hydroaminomethylation [6], [7], [8], [9], [10] are such processes for synthesis of amines with very high atom efficiency. Both these reactions have cheaper starting materials, an olefin and an amine. Hydroamination is still a very challenging reaction due to the very low TOF [11], [12], [13], [14], [15], [16]. Hydroaminomethylation is a reaction that has potential to develop for industrialization.

Hydroaminomethylation (Scheme 1) is the single pot synthesis of amines from an olefin, amine (alkyl amines, morpholine, pyrollidine etc.) and syngas (H₂, CO) [17], [18], [19]. It is an elegant, atom economic, efficient process for the synthesis of amines. Hydroaminomethylation has closer applications for the synthesis of nylon, drugs and various bulk and fine chemicals.

The study of this domino reaction has undergone progress in last decade with noteworthy contributions from the research groups of Eilbracht et al. [20], [21], [22], [23] and Beller and co-workers [24], [25]. The investigations in hydroaminomethylation showed that the hydroformylation catalyst can perform equally toward hydroaminomethylation reactions by tuning the reaction conditions [17]. A variety of rhodium based catalysts have been already found to be active for hydroaminomethylation [25], [26], [27], [28], [29], [30], [31], [32].

It is known that the homogeneous catalysts have the drawback of catalyst separation and recycling. Hydroaminomethylation currently performing in homogeneous condition also follows with the same. Hence a development of heterogeneous catalyst for hydroaminomethylation can contribute toward solving the above said problem. But the developments of catalyst system toward this route are scanty in literatures. There is a pressing need to develop catalyst system to carry out an economic, atom efficient and easily separable single pot synthesis of amines; however less attention is paid in this direction. Here we have attempted to heterogenize the well known HRh(CO)(PPh₃)₃ complex into the hexagonal mesoporous silica for hydroaminomethylation of olefins. HRh(CO)(PPh₃)₃ complex being well known for hydroformylation of olefins, its development into a heterogeneous catalyst would be an important concern. Investigation on various parameters like temperature, pressure, amount of the catalyst and olefin to amine substrate ratio are also performed.

Section snippets

Materials

Tetraethyl orthosilicate, dodecylamine, aminopropyl trimethoxysilane, hydridocarbonyl tristriphenylphosphine rhodium(I) were procured from Sigma–Aldrich, USA for the synthesis of catalyst. The reactants alkenes and amines were procured from Sigma–Aldrich, USA. H₂ and CO were procured from Ami Traders, Bhavnagar, Gujarat, India.

Synthesis of the support and functionalization

Hexagonal mesoporous silica (HMS) was synthesized according to the procedure reported elsewhere [33], [34]. The synthesized HMS was calcined at 650 °C for 6 h to remove the

Catalyst characterization

Low angle powder X-ray diffraction (PXRD) of calcined HMS, functionalized HMS and HRh(CO)(PPh₃)₃ encapsulated HMS were given in Fig. 1. These materials showed an intense reflection corresponding to 1 0 0 plane near 2θ values of 2–2.5° which corresponds to the formation of HMS [35], [36], [37], [38]. The intensities of the peak were decreased on functionalization and encapsulation process. This observation is due to the pore filling by functionalization and encapsulation. There had been a shift

Conclusions

Aminofucntionalized HMS was used as a support for encapsulation of Rh-complex and found to be an efficient catalyst for heterogeneous hydroaminomethylation reaction. A variety of alkenes and amines were tested for hydroaminomethylation activity of the catalyst. The catalyst could give 100% conversion with a very high selectivity of >95% to hydroaminomethylation products. Enamines were found in low amounts. The catalyst was tested for parametric variations study by taking 1-hexene and morpholine

Acknowledgments

Authors thank Council of Scientific and Industrial Research (CSIR), New Delhi, India for the financial support through Network Project on the Development of Specialty Inorganic Materials for Diverse Applications (NWP-0010). The authors also acknowledge Analytical Discipline and Centralized Instrument Facility, CSMCRI for providing instrumental analysis. NS acknowledge CSIR, New Delhi for the award of Senior Research Fellowship.

References (42)

K.S. Hayes
Appl. Catal., A
(2001)
M. Beller et al.
Chemosphere
(2001)
Y.Y. Wang et al.
Appl. Catal., A
(2004)
A.R. Smith et al.
Tetrahedron Lett.
(2012)
M. Khandelwal et al.
J. Organomet. Chem.
(2012)
G. Liu et al.
Tetrahedron Lett.
(2011)
A. Behr et al.
Tetrahedron Lett.
(2010)
C.S. Graebin et al.
Catal. Commun.
(2008)
A. Schmidt et al.
Tetrahedron
(2004)
V.K. Srivastava et al.
Catal. Commun.
(2009)

L. Routaboul et al.

Tetrahedron Lett.

(2005)

E. Petricci et al.

Tetrahedron Lett.

(2007)

Y.S. Lin et al.

Tetrahedron Lett.

(2001)

N. Sudheesh et al.

J. Mol. Catal. A

(2008)

N. Sudheesh et al.

J. Mol. Catal. A

(2010)

N. Sudheesh et al.

Appl. Catal., A

(2011)

A.M. Seayad et al.

Tetrahedron Lett.

(2003)

J. March

Advanced Organic Chemistry

(1992)

M. Beller et al.

Angew. Chem.

(1998)

M. Nobis et al.

Angew. Chem.

(2001)

Y.Y. Wang et al.

Green Chem.

(2006)

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Rhodium complex encapsulated functionalized hexagonal mesoporous silica for heterogeneous hydroaminomethylation

Abstract

Graphical abstract

Highlights

Introduction

Section snippets

Materials

Synthesis of the support and functionalization

Catalyst characterization

Conclusions

Acknowledgments

Appl. Catal., A

Chemosphere

Appl. Catal., A

Tetrahedron Lett.

J. Organomet. Chem.

Tetrahedron Lett.

Tetrahedron Lett.

Catal. Commun.

Tetrahedron

Catal. Commun.

Tetrahedron Lett.

Tetrahedron Lett.

Tetrahedron Lett.

J. Mol. Catal. A

J. Mol. Catal. A

Appl. Catal., A

Tetrahedron Lett.

Advanced Organic Chemistry

Angew. Chem.

Angew. Chem.

Green Chem.