New Compounds. Derivatives of Fluorene

A New Class of Singlet Carbene Ligands

“…11 Treatment with various phosphines or HMPA (HMPA=hexamethylphosphoric acid triamide) then gave the corresponding alkenyl phosphonium salts 3 a – d in respectable yields after ion exchange for the less coordinating BF 4 − (for the structures of two such salts in the solid state, see the Supporting Information) 12. Yet another possible carbene precursor 10 was obtained by condensation of the known ylide 9 13 with commercial 1‐methyl‐2‐formylbenzimidazole and N‐methylation of the resulting product with Meerwein salt (Scheme ).…”

Coordination complexes of aryl- and alkylphosphonium cyclopentadienylides (cyclopentadienylidene ylides), C5R4PR′R′′R′′′ (R=H, alkyl, aryl; R′, R′′, R′′′=alkyl, aryl)

“…The first successful synthesis of triphenylphosphonium fluorenylide was reported in 1947 by Pinck and Hilbert [47] who found that reaction of 9-bromofluorene with triphenylphosphine gave the corresponding phosphonium salt in nearly quantitative yield. The fluorenyl phosphonium salt was then deprotonated with aqueous ammonia to give the ylide as in Fig.…”

“…The fluorenyl phosphonium salt was then deprotonated with aqueous ammonia to give the ylide as in Fig. 10 [47].…”

“…Because of the ready availability of 9-bromofluorene, many derivatives of triphenylphosphoniumfluorenylide have been synthesized using this same methodology [47] and a variety of fluorenyl phosphonium ylides, with substitution of the phosphorus R groups, have been reported. In addition, 9-bromofluorene derivatives with substituents on the aryl rings have been used to give even more variety for this class of ligand [48].…”

Aryltriolborates as Air- and Water-Stable Bases for Wittig Olefination

“…1 The ylide is usually prepared by treating a phosphonium salt with a base and, depending on the nature of the phosphorus ylide, a variety of bases can be used. 2 While a stabilized ylide can be formed by using a weak base such as ammonium hydroxide, 3 triethylamine, 4 or potassium hydroxide, 5 a nonstabilized ylide, in particular Ph 3 P=C(R 1 )R 2 (where R 1 and R 2 = alkyl), often requires a strong base. For example, a literature search of the reaction of Ph 3 P + CHMe 2 (X -) with benzaldehydes revealed that the most commonly used base has been butyllithium, 6 with a few cases using potassium tert-butoxide, 7 sodium amide, 8 and potassium hexamethyldisilazide, 9 which are all airand/or water-sensitive compounds.…”