Regioselective, Stereoselective, and Conformationally Controlled Synthesis of (η⁴-Tetraarylcyclobutadiene)(η⁵-carbomethoxycyclopentadienyl)cobalt Metallocenes

Abstract

The Friedel-Crafts reaction of (η(4)-tetraphenylcyclobutadiene)(η(5)-carbomethoxycyclopentadienyl)cobalt with acid chlorides/aluminum chloride resulted exclusively in para-phenyl acylation. Both monoacylated (1.1 equiv of RCOCl/AlCl(3)) and tetraacylated products (>4 equiv of RCOCl/AlCl(3)) were synthesized. Reaction of PhCC(o-RC(6)H(4)) (R = Me, i-Pr) with Na(C(5)H(4)CO(2)Me) and CoCl(PPh(3))(3) gave predominantly (η(4)-1,3-diaryl-2,4-diphenylcyclobutadiene)(η(5)-carbomethoxycyclopentadienyl)cobalt metallocenes (1,3-[trans] vs 1,2-[cis] selectivity up to 6:1). Conformational control of Friedel-Crafts reactions on the major isomers gave exclusively para-acylation of the unsubstituted phenyl groups.

Synthesis of poly(1‐chloro‐2‐arylacetylene)s with high cis‐content and examination of their absorption/emission properties

“…Tri‐tert‐butylphosphine was received from Nippon Chemical Industrial Co. and used without further purification. ClCCC 6 H 5 , HCCC 6 H 4 ‐ o ‐ i Pr, HCCCC 6 H 4 ‐ p ‐NHC(O)O t Bu and ( t Bu 3 P) PdMeCl were synthesized according to the procedures in the literature. The solvents used for the air and moisture sensitive procedures were purified employing standard procedures.…”

Synthesis and Characterization of the Complete Series [(C5H5‐n Cln)Co(C4Ph4)] (n=1–5)

“…[12] An alternative "improved protocol for the synthesis" was therefore suggested, [9] that also allowed for large variations in the aryl moiety. The possibility to post-functionalize the phenyl rings was also reported [13,14] While the use of substituted cyclopentadienides (C 5 H 4 R) with R = CHO or COOMe allowed for a lot of post-functionalizations of the cyclopentadienyl ring, [1,5,6,8] it turned out much more difficult to post-functionalize the coordinated C 5 H 5 ring. [7] While mercuration with Hg(OAc) 2 /LiCl/ HClO 4 yielded mono-and/or dimercurated products [{C 5 H 5-n (HgCl) n }Co(C 4 Ph 4 )], [3,15,16] mercuration with Hg(OOCCF 3 ) 2 led to the formation of the pentamercurated [{C 5 (HgO 2 CCF 3 ) 5 } Co-(C 4 Ph 4 )].…”

Multiple Acetylation of Pentaphenylferrocene – Synthesis and Asymmetric Reduction of 1‐Acetyl‐1′,2′,3′,4′,5′‐penta(para‐acetylphenyl)ferrocene

“…All attempts to perform a Friedel–Crafts acylation on similarly bulky (η 5 ‐cyclopentadienyl)(η 4 ‐tetraphenylcyclobutadiene)cobalt have been reported to result in only a trace amount of cyclopentadienyl ring‐substituted product, and in our hands attempts at this reaction resulted in only decomposition of the starting material. However, following deactivation of the cyclopentadienyl ring of 6 by incorporation of an ester functionality, Friedel–Crafts acetylation could be performed on one or more of the phenyl groups giving, for example, compound 7 in 68 % yield (Scheme ) …”

“…Friedel–Crafts acetylation of (η 5 ‐carbomethoxycyclopentadienyl)‐(η 4 ‐tetraphenylcyclobutadiene)cobalt …”