Untitled

Migratory insertion of isocyanide into a ketenyl–tungsten bond as key step in cyclization reactions

“…Interestingly, related metal-free ketene formation by rearrangement of silyloxyalkynes was reported by Ponomarev. 53 The Tp′ congeners 2b-PF 6 and 4b {Tp′ = hydridotris(3,5-dimethylpyrazolyl)borate} were synthesized accordingly for improvement of XRD data. The identity of 3, 4a and 4b was determined by single-crystal XRD analysis.…”

Reactions of Boroles Formed by 1,1-Carboboration

“…We see the 19 F NMR signals of the B(C 6 F 5 ) 2 group and the single C 6 F 5 substituent and the 1 H/ 13 C NMR signals of the phenyl substituent at boron. The 13 C NMR resonances of the central five-membered heterocyclic core occur at δ 66.2 (CSi 2 ), 152.6, and 148.8 and at δ 56.9 for ring carbon atom (C1) of the exocyclic ketene unit . The ketene carbonyl carbon atom (CC21O) shows a typical 13 C NMR resonance at δ 179.2.…”

“…We found the unique ketene formation upon carbonylation of the borole 2 , a reaction that involves nucleophilic CO attack at the ring α carbon. Both of these cases might have profited from an enhanced electrophilic character of the central borole moiety in conjunction with the possibility to form key intermediates that contained a stabilized borata-ethene (i.e., α-boryl carbanion) type structural subunit. It seems that our new 1,1-carboboration entry into borole chemistry makes new derivatives of this interesting class of unsaturated cyclic π systems available which may show some uncommon reaction behavior.…”