FUNCTIONALIZATION OF 1,3-PHENYLENE-16-CROWN-5 VIA DIRECT LITHIATION

1,3-Phenylene-16-crown-5 (1) was selectively and quantitatively lithia ted at the intraannular 2-position with n-butyllithium, making functio nalization of this system easier than that of the 1,3-xylylene crown e thers. The lithiation yielded the corresponding (2-lithio-1,3-phenylen e)-16-crown-5 (2) without cleavage of the polyether ring. Subsequent r eaction with deuterium oxide, dimethyl disulfide, iodine, carbon dioxi de, dimethyltin dichloride (0.5 molar equiv), mercury dibromide (0.5 m olar equiv), benzyl bromide, and magnesium dibromide yielded (2-deuter io-1,3-phenylene)-16-crown-5 (3), [2-(methylthio)-1,3-phenylene]16-cro wn-5 (4), (2-iodo-1,3-phenylene)-16-crown-5 (5), (2-carboxy-1,3-phenyl ene)-16-crown-5 (6), methylbis[(1,3-phenylene-16-crown-5)-2-yl]stannan e (7), bis[(1,3-phenylene-16-crown-5)-2-yl]mercury (8), 2-benzyl-1,3-p henylene-16-crown-5 (9), and [2-(bromomagnesio)-1,3-phenylene]-16-crow n-5 (10), respectively. Functionalized analogues of this crown ether h ave not been reported previously. X-ray crystal structures of 6, 7, an d 10 were determined. According to the crystal structure of 6, the car boxylic substituent takes part in intramolecular hydrogen bonding with a transannular crown ether oxygen (O(8)). The crystal structure of 7 is the first one for a bis(crown ether)tin(IV) compound and reveals cl ose proximity between tin and four of the ten crown ether oxygens. In the Grignard reagent 10 the magnesium is hexacoordinated in a distorte d-octahedral fashion with the bromine and a THF oxygen in the apical p ositions and three of the five crown ether oxygens plus carbon C(1) in planar positions. It is the first example of a crown ether Grignard r eagent in which the metal center is not completely intramolecularly co ordinated.