Double Friedel–Crafts Acylation Reactions on the Same Ring of a Metallocene: Synthesis of a 2,5‐Diacetylphospharuthenocene

Abstract

The synthetic outcome of the Friedel-Crafts acylation of 1',2',3,3',4,4',5'-heptamethylphospharuthenocene reflects the nature of the acylating agent, with alkanoyl anhydride/trifluoromethanesulfonic acid (TfOH) reagents giving monosubstitution at the phospholyl ring, whereas alkanoyl chloride/AlCl(3) gives 2,5-disubstitution. DFT calculations indicate that this unusual double acylation can be facilitated by the intervention of the phosphorus atom at an early stage in the reaction trajectory, with the acyl group being delivered from the phosphorus atom into the ring 2- or 2,5-positions.

Oligo(metallocene)s Containing Keto‐Bridged Phospholyl Rings

“…An X‐ray diffraction analysis (Figure 3) confirmed the anticipated configuration of 10 . The long phosphametallocene–acyl distances observed in the structural analysis lie in the normal range for this class of complexes30 and imply low rotation barriers about the ketone group (which have been shown by Klys and Zakrzewski to be of the order of ca. 10 kcalmol –1 );35,36 more linearly disposed conformers are therefore likely to be readily accessible through low‐energy rotations.…”

“…The study here is interesting because the interception of a quite strongly bound intermediate 9 sheds some light upon the reaction trajectory for the coordination of phospholide anions to late transition metal centres and also provides a rationale for a near‐perfect diastereoselectivity that is observed during the formation of 10 . Strong literature evidence suggests that the reaction of phospholide anions with late transition metal complexes involves the transient formation of η 1 ‐coordinated phospholides,30–33 and this incipient η 1 ‐coordination might reasonably be expected to impose a degree of selectivity upon the reaction trajectory for the incoming metal centre. In situ NMR spectroscopic studies showed that careful treatment of phospholide 8 with two equivalents of [FeCp*(Cl)tmeda] under mild conditions (THF, 25 °C) led to complex intermediate 9 (Figure 2) quantitatively, but isolation proved difficult and single crystals suitable for characterisation could only be obtained in low yield.…”

“…All operations were performed either by using cannula techniques on Schlenk lines under an atmosphere of dry nitrogen or in a Braun Labmaster 130 drybox under dry purified argon. Compounds 4 and 7 were prepared according to protocols described previously,30 and [FeCp*Cl(tmeda)] was prepared according to Jonas 39. Solvents were distilled under dry nitrogen: THF and diethyl ether from sodium benzophenoneketyl, pentane from sodium benzophenoneketyl/tetraglyme, methanol from sodium methoxide and dichloromethane from P 4 O 10 .…”

A Self‐Assembling Ligand Switch That Involves Hydroxide Addition to an sp2 Hybridised Phosphorus Atom – A System Allowing OH– Mediated Uptake of [MCl2] (M = Pd, Pt) Centres

“…Treatment of rac ‐ 1 with [PdCl 2 (1,5‐cod)] in freshly distilled, phosphorus pentoxide‐dried CH 2 Cl 2 gave no discernible reaction over 24 hours at ambient temperature; however, in water‐saturated CH 2 Cl 2 , the robust, air‐stable phosphinite complex rac‐ 4 was obtained instantly. No other species were detectable in solution by 31 P NMR spectroscopy, and some indication of the nature of the hydroxide ion binding was provided by clear and distinct 31 P resonances ( δ = 8.3, –177.8 ppm, 2 J PP = 196 Hz) that confirm non‐fluxionality on the NMR timescale …”

Trifluoromethanesulfonic Acid as Acylation Catalyst: Special Feature for C- and/or O-Acylation Reactions

“…of the conventional catalyst AlCl3 at room temperature [28] or at ~50 °C [29]. This system has been extended for the use of a limited number of possible acylation positions for metallocenes 47 and 48 [30]. Monosubstitution of an acyl group at the two-position ( [23,24]; to address these limitations, TfOH has been utilized [25].…”