Synthesis of (Bromo-η ⁴-2-pyrone)tricarbonyliron Complexes

Abstract

S y n t h e s i s o f ( B r o m o -h 4 -2 -p y r o n e ) t r i c a r b o n y l i r o n C o m p l e x e sAbstract: The addition of the tricarbonyliron 'Fe(CO) 3 ' unit to several bromo-substituted 2-pyrones has been investigated. Direct reaction with Fe 2 (CO) 9 in benzene at 80 ºC results in poor yields and hydrodebromination. Switching the solvent to n-Bu 2 O, sequential addition of Fe 2 (CO) 9 and slow passage of N 2 through the solution improves the yields of the tricarbonyliron complexed 2-pyrones. Direct 'Fe(CO) 3 ' transfer reagents such as (h 4 -benzylideneacetone)tricarbonyliron or generic (h 4 -1-azabuta-1,3-diene)tricarbonyliron complexes, under both stoichiometric and catalytic conditions, fails to give the desired complexes. Surprisingly, the unstable bis(h 2 -cis-cyclooctene)Fe(CO) 3 (Grevels' reagent) did serve as a useful transfer reagent.

Bioactive Properties of Iron-Containing Carbon Monoxide-Releasing Molecules

“…As shown, the common denominator of all compounds is a 2-pyrone ring which is coordinated to an irontricarbonyl complex [Fe(CO) 3 ] and has different ring substituents, such as halogens (Cl or Br) and methyl groups (Me). These irontricarbonyl complexes were synthesized according to a general procedure described previously (Fairlamb et al, 2003).…”

Bis(triphenylphosphine)palladium(II)phthalimide – an easily prepared precatalyst for efficient Suzuki–Miyaura coupling of aryl bromides

“…Lowering catalyst loadings also reduces the amount of trace quantities of palladium present in the final products. In recent work, we have applied Suzuki-Miyaura methodology to the synthesis of novel chemotherapeutic agents based on the 2-pyrone-ring system [45][46][47][48]. The electrophilic partner is 4-bromo-6-methyl-2-pyrone 2h, which we have established is a relatively activated substrate.…”

“…The following compounds characterized by 1 H, 13 C NMR spectroscopy and mass spectrometry are known within the literature: biphenyl 4a [52], 4-methylbiphenyl 4b [45], 4 -formylbiphenyl 4c [53], 4-chlorobiphenyl 4d [46] 4-acetylbiphenyl 4e [54], 4-acetyl-4 -methylbiphenyl 4f [55], 4-acetyl-4 -formylbiphenyl 4g [56], 4-acetyl-4 -chlorobiphenyl 4h [57], 4-nitrobiphenyl 4i [58], 4-nitro-4 -methylbiphenyl 4j [59], 4 -nitro-biphenyl-4-carbaldehyde 4k [60], 4-nitro-4 -chlorobiphenyl 4l [61], 2-methoxybiphenyl 4m [62], 3-(2-methoxyphenyl)thiophene 4n [63], 2-methoxy-trans-stilbene 4o [64], 2-methoxycarbonylbiphenyl 4p [65], 3-(2-methoxycarbonylphenyl)thiophene 4q [66], 2-methoxycarbonyl-trans-stilbene 4r [67], 2,6-dimethylbiphenyl 4s [68], 2,6-dimethyl-4 -methylbiphenyl 4t [42], 2,6-dimethyl-4 -formylbiphenyl 4u [42], 2,6-dimethyl-4 -chlorobiphenyl 4v [69], 4-bromo-6-methyl-2-pyrone 2h [48], 4-phenyl-6-methyl-2-pyrone 4w, 4-(4 -methylphenyl)-6-methyl-2-pyrone 4x [48], 4-(4 -formylphenyl)-6-methyl-2-pyrone 4y [48], 4-(4 -chlorophenyl)-6-methyl-2-pyrone 4z [48], 4-(2 -phenyl-trans-ethenyl)-6-methyl-2-pyrone 4ab [48]. …”

A synthetic, structural and reactivity study of [(η4-C4R4)Co(η5-C5H4X)] complexes, R=Me or Et; X=CHO, CHCHFc, CHCH(η5-C5H4)Co(η4-C4Ph4), CHC(CN)2: Unexpected formation of [(η5-cyclopentadienyl)(η4-3,4,5,6-tetraethyl-α-pyrone)cobalt]

“…During the synthesis of [(g 5 -C 5 H 4 CHO)Co(g 4 -C 4 Et 4 )], 5, via Route 1, for which the first step is the reaction of sodium cyclopentadienide with ethyl formate, an unexpected minor side product was characterised by X-ray crystallography as the tetraethyl-a-pyrone complex, 18. Certainly, pyrones are wellknown ligands: (a-pyrone)Fe(CO) 3 was generated as a side-product in the preparation of [(g 4 -C 4 H 4 )Fe(CO) 3 ] from Fe(CO) 5 and a cyclobutene complex [41], and as the main product from the reaction of a-pyrone and Fe(CO) 5 ; numerous other preparations have also been described [42][43][44][45][46][47][48]. Although the generation of cyclobutadienes by elimination of carbon dioxide from a-pyrones is well established [48,49], the reverse process would appear to be less viable.…”

“…The eluant was concentrated, and precipitation with pentane gave (g 4 -C 4 Et 4 )Co(CO) 2 I (1) (3.93 g, 9.7 mmol; 45%) as a red-brown solid, m.p. 45 …”