Iron carbonyl promoted conversion of .alpha.,.omega.-diynes to (cyclopentadienone)iron complexes

Abstract

An efficient high-yielding procedure is described for the intramolecular carbonylative coupling of , -diynes to give cyclopentadienone-Fe(CO)3 complexes. Exchanging one CO ligand with PPh3 affords control over the manipulation of , '-trimethylsilyl-substituted cyclopentadienone complexes. The preparation of , -diynes with a hydroxy group adjacent to one alkyne unit leads to modest stereocontrol upon cyclization forming the Fe(CO)3 complex. The hydroxy-substituted complex was oxidized to ketone. Borohydride reduction and Grignard addition to the ketone proceed anti to the Fe(CO)3 moiety. The X-ray crystal structure of C^H^FeOsP shows that it crystallizes in the monoclinic space group 2 / in a unit cell of dimensions a = 12.0595 ( 24), b = 13.3926 (30), c = 19.0682 (38) k, ß -93.98 (2)°, with Z = 4. moieties accompanied by the insertion of carbon monoxide.1 Historically, the iron carbonyl mediated cyclization of acetylenes to form cyclopentadienone (CPD) complexes has been, with few exceptions, an inefficient process. Early reports cite the preparation of CPD tricarbonyliron complexes from phenyl-and diphenylacetylene in very low yields (<15%).2 Only in cases where the R group is (1)

Microwave-assisted synthesis of cyclopentadienone iron tricarbonyl complexes: molecular structures of [{η4-C4R2C(O)C4H8}Fe(CO)3] (R = Ph, 2,4-F2C6H3, 4-MeOC6H4) and attempts to prepare Fe(II) hydroxycyclopentadienyl–hydride complexes

“…Heating a 1:2 mixture of the diyne and Fe(CO) 5 in a microwave reactor tube for 15 min resulted after cooling, venting, filtration and flash chromatography in the isolation of the desired cyclopentadienone complexes [{η 4 -C 4 R 2 C(O) C 4 H 8 }Fe(CO) 3 ] (1-5) as yellow crystalline solids in 70-80% yields (Scheme 3). Yields of 1 and 2 are significantly higher than those of 57 and 52%, respectively, reported previously [46][47][48], suggesting that the significantly lower reaction times lead to less product decomposition. While we generally carried out reactions using 0.8 mmol of diyne, we noted similar yields when the reaction scale was doubled along with the irradiation time.…”

“…In other complexes of this type, it is generally the central carbon-carbon bond, C(6)-C(7), which is the shortest within the ring. This is also the case for 4 (both independent molecules) and 3 [C(6)-C(7) 1.421-1.429 Å; C(5)-C(6) and C(7)-C(8) 1.432-1.453 Å] and has been attributed to the back-bonding interaction between the metal centre and the diene LUMO [46][47][48]. The situation is less clear in 2 where the C(6)-C(7) bond length of 1.430(2) Å is shorter than the C(7)-C(8) interaction of 1.446(2) Å but comparable to the C(5)-C(6) vector of 1.429(2) Å.…”

“…The synthetic methodology developed by Pearson and coworkers in the early 1990s for the conversion of 1,6-diynes, RC≡C(CH 2 ) n C≡CR (n = 3-5) into cyclopentadienone iron tricarbonyl complexes involves heating with a fivefold excess of Fe(CO) 5 in toluene at 125-130 °C for 24 h under 100 psi of carbon monoxide [46][47][48]. Over the past 20 years, few developments have been made to this procedure, with Wills and co-workers recently reporting the use of similar conditions for the low-moderate-yield synthesis of some related complexes [17], although a CO pressure was not required.…”

(Cyclopentadienone)iron Shvo Complexes: Synthesis and Applications to Hydrogen Transfer Reactions

“…Reactions were monitored by TLC using aluminum backed silica gel 60 (F254) plates, visualized using UV 254 nm and phosphomolybdic acid 20 4-phenyl-3-butyn-2-yloxy(prop-2-yne) 12b, 21 3-phenyl-2-propyn-1-yloxy(prop-2-yne) 12a, 22 3-phenyl-2-propyn-1-yloxy(3-phenylprop-2-yne) 13a, 23a 4-phenyl-3-butyn-2-yloxy(3-phenylprop-2-yne) 13b, 21 tricarbonyl(2,4-bis(trimethylsilyl)bicyclo[4.3.0]nona-1,4-dien-3-one)iron 6. 8 …”

Asymmetric catalysis using iron complexes – ‘Ruthenium Lite’?

“…This 35 remains to be tested experimentally. Although a racemic process, a very significant breakthrough was reported in 2007 by Casey and Guan, 24,25,3 who found that the known 26,27 cyclopentadienyl iron hydride complex 11, itself prepared from the iron tricarbonyl cyclone complex 12, was effective at the catalysis of carbonyl and imine 45 hydrogenation under relatively mild conditions (Figure 4). There are analogies in the speculated mechanism of the catalytic cycle to that of the reactions catalysed by the ruthenium-based Shvo catalyst 13, which has also been extensively studied by complex.…”