The first racemization-stable helicene derivatives fluorinated at terminal rings, 1,2,3,4-tetrafluoro[6]helicene (6) and 1,2,3,4,13,14,15,16-octafluoro[6]helicene (15), were synthesized via the Wittig reaction followed by oxidative photocyclization in an overall yield of 41% of 6 and 76% of 15. The changed electronic structure in fluorinated helicenes was reflected in a slight shift of UV–vis absorption
The synthesis of 2-bromo[6]helicene was revised and improved up to 51% yield. Its reactivity was thoroughly investigated, and a library of 17 different carbon, boron, nitrogen, phosphorus, oxygen and sulfur substituted derivatives was prepared. The racemization barrier for 2-bromo[6]helicene was determined, and the usage of enantiomers in the synthesis of optically pure helicenes was rationalized.
Photochemistry with circularly polarized light—III
作者:A. Moradpour、H. Kagan、M. Baes、G. Morren、R.H. Martin
DOI:10.1016/0040-4020(75)80209-2
日期:1975.1
A systematic study of the photochemical ring-closure of bis(arylvinyl)arenes, using circularly polarized light, is described and commented. In the two series of compounds 5a–e and 6a–e, the observed optical yields follow a similar trend; no asymmetric syntheses were observed in the case of the higher benzologues of [10] helicene, using a 290–370 nm irradiation band, circularly polarized at 313 nm.
synthetic strategy toward phosphahelicenes containing a terminal phosphinine ring has been explored. The 4-phenyl-6-methyl-2-phospha[7]helicene was prepared from starting 2-bromobenzo[c]phenanthrene in 12% overall yield in 12 steps. The synthetic approach involves introduction of the phosphorus function prior to photocyclization forming the final helicene skeleton, followed by the formation of a phosphorus
已经探索了针对含有末端膦环的磷酸螺旋烯的合成策略。4-phenyl-6-methyl-2-phospha[7]helicene 由起始 2-溴苯并[ c ]菲在 12 个步骤中以 12% 的总产率制备。合成方法包括在光环化形成最终的螺旋骨架之前引入磷功能,然后形成磷六环。通过 X 射线晶体学证实了具有末端膦环的第一个 phosphahelicene 的结构。