Synlett 2007(20): 3127-3130  
DOI: 10.1055/s-2007-992380
LETTER
© Georg Thieme Verlag Stuttgart · New York

A Convenient One-Pot Synthesis of 2,2-Dialkyl-2,3-dihydro-1H-naphtho[2,1-b]pyrans

Amitabh Jha*, Po-Jung Jimmy Huang, Chandrani Mukherjee, Nawal K. Paul
Department of Chemistry, Acadia University, Wolfville, NS, B4P 2R6, Canada
Fax: +1(902)5851114; e-Mail: ajha@acadiau.ca;
Further Information

Publication History

Received 28 August 2007
Publication Date:
21 November 2007 (online)

Abstract

This work describes a convenient one-pot procedure for the synthesis of 2,2-disubstituted 2,3-dihydro-1H-naphtho[2,1-b]pyrans {i.e. 2,2-disubstituted 1H-benzo[f]chromans} by the reaction of 2-tetralones and α,α-disubstituted β-hydroxy propionaldehydes under acidic conditions.

10

In a typical procedure, a mixture of an appropriate β-hydroxypropionaldehyde (0.01 mol) and a 2-tetralone analogue (0.0105 mol) were stirred in AcOH (ca. 50 mL) at 0 °C. Freshly prepared dry HCl gas was briskly passed through the mixture for 1 h. Stirring was continued at r.t. for 17 h. Then, AcOH was removed under vacuum and the residue was extracted with CH2Cl2 (2 × 100 mL) and H2O (2 × 50 mL). The organic layer was dried and rotary evaporated to dryness to yield crude product, which was purified by column chromatography (silica gel mesh size 230-240; eluent 1-2% EtOAc-hexane). Spectroscopic Data for a Representative Compound
Compound 4o: 1H NMR (300 MHz, CDCl3): δ = 1.53 (3 H, s, CH3), 3.10 and 3.46 (1 H each, d, J = 16.2 Hz, ArCHa and ArCHb), 3.97 (3 H, s, OCH3), 4.19 and 4.33 (1 H each, d, J = 10.5 Hz, OCHa and OCHb), 6.99 (1 H, d, J = 8.7 Hz, ArH), 7.08 (1 H, m, ArH), 7.15 (1 H, s, ArH), 7.32 (1 H, d, J = 6.9 Hz, ArH), 7.39-7.50 (4 H, m, ArH), 7.61 (1 H, d, J = 8.7 Hz, ArH), 7.73 (1 H, d, J = 8.7 Hz, ArH) ppm. 13C NMR (75 MHz, CDCl3,): δ = 25.00, 35.84, 36.36, 55.75, 74.42, 101.48, 112.70, 115.65, 116.56, 124.80, 126.31, 127.09, 127.91, 129.03, 130.51, 134.82, 146.17, 152.33, 158.81 ppm. IR (KBr): ν = 2963, 1624, 1515, 1233, 1222, 1028, 830, 699 cm-1.