Versuche zur Synthese von [2.2]- und [2.3]Cyclopentadienophanen

Abstract

Synthetic Attempts towards [2.2]‐ and [2.3]Cyclopentadienophanes. The first [2.2]Cyclopentadienophane (=2,2,3,3,8,8,9,9‐octamethyltricyclo[8.2.1.14,7]tetradecatetraene; 1b) has been synthesized (Scheme 5) by reductive coupling of 6,6‐dimethylfulvene 3→5 (50%) followed by base‐induced twofold condensation of 1,2‐di(cyclopentadienyl)‐1,2‐dimethylbutane 5 with acetone to give difulvene 15 (95%). Reductive coupling of 15 gives a complex mixture of tautomers of 16, 17, and 1b, which contains ca. 50% of the target molecule 1b. Other synthetic attempts towards [2.2]cyclopentadienophanes 1a and 1b and [2.3]cyclopentadienophane 18 are discussed.

An iron-cyclopentadienyl bond cleavage mechanism for the thermal ring-opening polymerization of dicarba[2]ferrocenophanes

“…To this end, a sample of dicarba [2]ferrocenophane meso-[Fe (h 5 -C 5 H 4 ) 2 (CHCy) 2 ] meso-13 (Cy ¼ cyclohexyl, melting point ¼ 149-151 C), prepared via a metathesis reaction of FeCl 2 with meso-Li 2 [(C 5 H 4 ) 2 (CHCy) 2 ], 33,34 was sealed in a glass tube under vacuum and heated with rocking at 300 C for 1 h. Typical thermal ROP experiments for [n]ferrocenophanes involve an increase in viscosity followed by immobilization of the melt upon polymerization. 11,35 In this experiment, the solid sample of meso-13 melted and remained mobile for the duration of the thermolysis experiment.…”

Photocontrolled Ring‐Opening Polymerization of Strained Dicarba[2]Ferrocenophanes: A Route to Well‐Defined Polyferrocenylethylene Homopolymers and Block Copolymers

“…6‐ iso ‐Propylfulvene was prepared by the method of Little and Stone 46. The flytrap ligand Li 2 [(C 5 H 4 ) 2 (CH i Pr) 2 ] was synthesized by Na‐mediated reductive dimerization of 6‐ iso ‐propylfulvene following the procedure of Neuenschwander and co‐workers 47. Li[C 5 H 4 Me] was prepared by cracking dimethyldicyclopentadiene and deprotonation by using n BuLi.…”