Chiral 1,10‐Phenanthroline‐Bridged Calix[6]arenes

Abstract

Several approaches to chiral derivatives of the 1,10-phenanthroline-bridged calix[6]arene 3 have been investigated, and seven new chiral calix [6]arenes have been synthesized. The C 2 -symmetric axially chiral bimacrocycle 5 has been synthesized as racemic mixture; calixarenes 8, 14, 18, 19, 20 and 21 carrying chiral substituents (camphorsulfonyl, myrtanyl) have been prepared using enantiomerically pure reagents.

Concave 1,10‐Phenanthrolines as Ligands for Cyclopropanations – Towards a Deeper Understanding of the Stereoselectivity

“…For this reaction, a diastereomeric ratio of 32:68 (endo/exo) is reported. [8] Through the use of 1,10-phenanthroline ligands, this diastereoselectivity can be changed [8,11,16,17,18] either towards exo or towards endo products (see Introduction). Table 5 compares the selectivities of the new ligands 3 and 4 with those of other 1,10-phenanthrolines in the copper(I)-catalysed cyclopropanation of indene (28).…”

“…2,9-Diiodo-1,10-phenanthroline (12) was synthesised by the well known procedure described by Lewis et al [20] and Yamada et al [21] From 1,10-phenanthroline (5), chloro atoms were first introduced at the 2-and 9-positions to yield phenanthroline 10, and then a chloro-iodo exchange was accomplished (see Figures 3 and 4). The different phenylboronic acids 17 and 20 were synthesised from resorcinol (13) or from 4-bromophenol (18). Resorcinol (13) was first halogenated with iodine monochloride to yield the desired product, 4-iodoresorcinol (14b), in about 40 % yield.…”

“…[14,15] The last two classes have been employed as ligands in copper(I)-catalysed cyclopropanations of alkenes such as styrene or indene with diazoacetates; [8,11,16,17,18] some re- markable selectivities have been achieved. Whereas the cyclophane-derived ligands 1 exhibited strong anti selectivities (up to 140:1), the calixarene derivatives 2 were able to produce the syn products predominantly (best value: 86:14).…”

Bimacrocyclic NHC transition metal complexes

“…After 16 h, the mixture was passed through a short pad of silica gel and the silica gel was rinsed with diethylether (20 mL). The filtrate was then filled up to 25 mL with diethylether and analyzed by GC, following an established procedure [34]; conditions: split ratio 11:1, injector temp. 250°C, detector temp.…”