3-(3-Fluorobenzyl)-1H-isochromen-1-one

The asymmetric unit of the title compound, C16H11FO2, contains two independent molecules. The isochromene ring systems are planar and are oriented with respect to the fluorobenzene rings at dihedral angles of 87.15 (3) and 87.85 (3)° in the two molecules.

The asymmetric unit of the title compound, C 16 H 11 FO 2 , contains two independent molecules. The isochromene ring systems are planar and are oriented with respect to the fluorobenzene rings at dihedral angles of 87.15 (3) and 87.85 (3) in the two molecules.

Comment
Isocoumarins are secondary metabolites derived from the acetate pathway and are structurally related to the coumarins, but with an inverted lactone ring (Hill, 1986). They are produced by microorganisms, insects and some higher plants, and have a wide range of biological activities, including antitumoral, antileucemic, antiviral and antimicrobial (Hill, 1986;Canedo et al., 1997;Whyte et al., 1996). Isocoumarins (Barry, 1964) are also useful intermediates in the synthesis of a variety of important compounds including some isoquinoline alkaloids. In view of their natural occurrence, biological activities and utility as synthetic intermediates, we have synthesized the title compound, and reported herein its crystal structure.
The asymmetric unit of the title compound contains two crystallographically independent molecules of similar geometry (Fig 1). The bond lengths (Allen et al., 1987) and angles are within normal ranges and comparable with 3-(2chlorobenzyl)isocoumarin (Abid et al., 2006).

Experimental
A mixture of 3-fluorophenylacetic acid (5 g, 32 mmol) and thionyl chloride (2.94 ml, 34 mmol) was heated for 30 min in the presence of a few drops of DMF under reflux at 343 K to give 2-(3-fluorophenyl)acetyl chloride. Completion of reaction was indicated by the disappearance of gas evolution. Removal of excess thionyl chloride was carried out under reduced pressure to afford 2-(3-fluorophenyl)acetyl chloride. Homophthalic acid (1.3 g, 7.2 mmol) was then added and the solution was refluxed for 4 h at 473 K with stirring. The reaction mixture was extracted with ethyl acetate (3 × 100 ml), and an aqueous solution of sodium carbonate (5%, 200 ml) was added to remove the unreacted homophthalic acid. The organic layer was separated, concentrated and chromatographed on silica gel using petroleum ether (313-353 K fractions) as eluent to afford the title compound (yield; 72%, m.p. 447-448 K). Single crystals suitable for X-ray analysis were obtained by slow evaporation of an ethyl acetate solution.

Refinement
H atoms were positioned geometrically, with C-H = 0.93 and 0.97 Å for aromatic and methylene H, respectively, and constrained to ride on their parent atoms with U iso (H) = 1.2U eq (C).
supplementary materials sup-2 Figures Fig. 1. The molecular structure of the title molecule, with the atom-numbering scheme. Displacement ellipsoids are drawn at the 30% probability level.