Reactions of calix[4]arenes with 1,3-dibromopropane and 1,5-dibromopentane. Identification of products using 1D and 2D NMR techniques, and X-ray crystallography

• Preparations of a new biscalixarene and three novel calixarenes are reported.
• The compounds are characterized by MS and various NMR spectroscopy techniques.
• Single-crystal X-ray diffraction was determined for some of the calixarenes.
• NOESY spectrum of calixarene 10 suggests the preferred solution conformation is that of the X-ray.
• Monobridged calixarene 13 was assigned completely by NMR and MS, using HMBC to map out the carbon skeleton.

Attempts to bridge a calix[4]arene with a three-carbon bridge using 1,3-dibromopropane and NaH/DMF led to elimination reactions. Using K2CO3/CH3CN, three new calixarenes were obtained: a biscalixarene (8), a novel bridged calixarene (9), and a partial cone calixarene (10). Attempts to bridge a calix[4]arene with a five-carbon bridge using 1,5-dibromopentane and K2CO3/CH3CN led to a (known) biscalixarene (12) and a novel monobridged calixarene (13). To characterize the new calixarenes, a variety of 1D and 2D NMR techniques, mass spectrometry, and in some cases X-ray crystallography were used.

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