Tetrahedron Lam. Vo131, No.4-1, pp bl53-bl56.1990 Rited in Great Britain MOLECULRSFOR lNTRAMOLECULARRRCOGNlTION. SYNTHESISANDSTRU~RESOFDIARYGANDARYLN~~YLETHYNE Kevin L. Evans, Philippe Prince, Enoch T. Huang’, Keisha R Bossl and Richard D. Gandour* Department of Chemistry, Louisiana State University Baton Rouge, Louisiana 70803-1804 Summorp: While synthesizing m0d& for intramolecular recognition, a simpk and qJicient method for forming terminal arylethynes was developed and pallmiium-catalyzed coupling chemistry of alkynes with either aryl iodkies or atyl tnflates MU used to fonn crowakd disubstituted al&es. Intramolecular recognition describes the interaction of two groups on the same molecule. As such it encompasses intramolecular catalysis in small molecules, proteins, and DNA, and non-covalent interactions that stabilize the terdary structum of biopolymers and those that regulate nanometric devices. We are synthesizing a series of diaql- and arylnaphthylethynes, 1 - 3, for studies of intramoleculiu recognition. Others have used this framework to anchor functional groups in a defiued geometry for complexation of cations.3 We report herein an efficient synthesis of these crowded ethynes by combining a modification of a classic method for the synthesis of terminal alkynes with a modem organometallic method for the synthesis of disubstituted alkynes. 1 R=H 3 2R=OCH3 We have developed a simple method for synthesizing electron-rich aryle.thynes. (Scheme 1) Our first attempt to convert 2’,6’-dimethoxyacetophenoue 4a into the corresponding alkyne 6a following a classic pro&me’ resulted in undesired products. Two concumnt reactions took place between the electron-rich acetophenone 4a and phosphorus pentachknide - - formation of a vinyl chloride and chlorination of the aromatic ring. Dehydmhalogenation of this product by lithium diiqropylamide pmduced lchloro-3- ethynyl-2,4-dimethoxybenzenes. To prevent chlorinating the ring, a five- to seven-fold excess of phosphorus trichloride is mixed with the ketone in benzene before phosphorus pentachloride is added to the solution6. Quantitative conversion, based on NMR data, of the ketone into the vinyl chloride is accomplished without chlorinadug the ring. We 6753