An Efficient One-Pot Synthesis of Substituted 1H-Naphtho[2,1-b]pyrans and 4H-1-Benzopyrans (¼ Chromenes) under Solvent-Free Microwave-Irradiation Conditions by Adimulam Chandra Shekhar a ), Akula Ravi Kumar a ), Gangaram Sathaiah a ), Kengiri Raju a ), Pamulaparthy Shanthan Rao* a ), Madabhushi Sridhar a ), Banda Narsaiah a ), Punnamraju Venkata Satya Surya Srinivas a ), and Balasubramanian Sridhar b ) a )Fluoroorganics Division, Indian Institute of Chemical Technology, Tarnaka, Hyderabad 500607, India (phone/fax: þ 91-40-27193185; e-mail: shanthanpp1954@gmail.com) b )Department of X-ray Crystallography, Indian Institute of Chemical Technology, Tarnaka, Hyderabad 500607, India A facile heterogeneous synthesis of 3-amino-1-aryl-1H-naphtho[2,1-b]pyran and 2-amino-4-aryl- 4H-1-benzopyran derivatives 3 and 5, respectively, was carried out efficiently by one-pot three- component coupling of an aromatic aldehyde 1, an active methylene compound 2, and naphthalen-2-ol or a phenol 4 in the presence of 5- molecular sieves under solvent-free microwave-irradiation conditions ( Scheme 1 and 2, Tables 1 and 2). The catalyst was recovered and recycled ( Table 3). Introduction. – Substituted chromenes (¼ benzopyrans) are important compounds due to their applications in pigments, cosmetics, and agrochemicals, and also they are integral part of many natural products [1 – 5] and many therapeutic agents such as antibacterials [6], antivirals [7], mutagenics [8], and antitumor [9] and CNS-active agents [10]. Conventional method for the synthesis of substituted chromenes are mainly based on benzaldehyde, malononitrile, and naphthalen-2-ol by using various catalysts viz., cetyltrimethylammonium chloride (CTACl) [11], benzyltrimethylammo- nium chloride (TEBA) [12], K 2 CO 3 [6], g-alumina [13], piperidine [14], TiCl 4 [15], 1,8- diazabicyclo[5.4.0]undec-7-ene (DBU) [16], ceric ammonium nitrate (CAN) [17], methyltrioctylammonium chloride (Aliquat  336) [18], or CaNa 2 P 2 O 7 [19]. However, all these methods have disadvantages in terms of cost, longer reaction times, complex workup procedures, and usage of solvents. As a result, they are not environmentally benign, and hence, there is an urgent need to develop an efficient ecologic method for the synthesis of benzochromene (¼ naphthopyran) derivatives. Results and Discussion. – In continuation of our efforts in the synthesis of heterocyclic bioactive molecules by efficient procedures, we wish to report herein a three-component one-pot synthesis of 1H-naphtho[2,1-b]pyrans (¼ benzo[ f ]- chromenes) 3 from naphthalen-2-ol, an aldehyde 1, and an active methylene compound 2 in the presence of 5- molecular sieves (MS) as catalyst under solvent-free microwave-irradiation (MWI) conditions ( Scheme 1). A model reaction was per- formed with stoichiometric quantities of benzaldehyde (1a) , malononitrile (2,X ¼ CN) and napththalen-2-ol in the presence of a catalytic amount of finely powdered 5- Helvetica Chimica Acta – Vol. 95 (2012) 502  2012 Verlag Helvetica Chimica Acta AG, Zürich