| Budget Amount *help |
¥3,100,000 (Direct Cost: ¥3,100,000)
Fiscal Year 2006: ¥1,000,000 (Direct Cost: ¥1,000,000)
Fiscal Year 2005: ¥2,100,000 (Direct Cost: ¥2,100,000)
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| Research Abstract |
One of the most useful chiral phosphine ligands is 2,2'-bis(diphenylphosphino)-1,1'-binaphthyl (BINAP), which exhibits high enantioselectivity in several types of asymmetric reactions including ruthenium-catalyzed hydrogenation and rhodium-catalyzed 1,4-addition and its related reactions. Over the last decade, there have been major efforts to prepare BINAP derivatives for recycling catalytic systems and achieving higher selectivity in asymmetric synthesis. Most of these BINAP derivatives have been prepared in several steps starting from 6-or 6,6'-substituted 1,1'-bi-2-naphthol. However, these derivatizations are inferior to direct functionalization of BINAP due to their low yields and associated handling losses. Here we report a new facile regioselective iodination at the 5,5'-position of BINAP and subsequent Sonogashira coupling reaction leading to the ethynyl-BINAP which is useful as a chiral ligand for a rhodium-catalyzed asymmetric 1,4-addition. Bis(pyridine)iodonium tetrafluoroborate was successfully used for regioselective iodination of BINAP dioxide to give 5,5'-diiodoBINAP dioxide in excellent yield of 92%, with no observed formation of 4,4'-diiodoBINAP dioxide. A Sonogashira cross-coupling reaction with 5,5'-diiodoBINAP dioxide gave the desired bis(phenylene-ethynylene) products in good yield. The resulting 5,5'-disubstituted BINAP dioxides have excellent fluorescent properties. Furthermore, we examined to transform 5,5'-disubstituted BINAP dioxides to sol-gel precursors with allylsilyl groups giving chirally photochemical materials. It is confidently expected that these chiral sol-gel precursors open the new field of material chemistry.
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