Abstract:The addition of carbon and heteroatom nucleophiles to (bicyclo[5.1.0]octadienyl)Fe(CO)(2)L(+) cations 5 or 8 (L = CO, PPh(3)) generally proceeds via attack at the dienyl terminus on the face of the ligand opposite to iron to generate 6-substituted (bicyclo[5.1.0]octa-2,4-diene)iron complexes (11 or 13). In certain cases, these products are unstable with respect to elimination of a proton and the nucleophilic substituent to afford (cyclooctatetraene)Fe(CO)(2)L (4 or 7). Decomplexation of 13f, arising from addit… Show more
“…The internal dienyl hydrogens H 2 and H 2 ‘ coalesce at −10 °C, corresponding to k c = 349 s -1 and Δ G ⧧ =12.8 kcal mol -1 . This activation energy is comparable with that found for apical−basal phosphite exchange in (cyclohexadienyl)Fe(CO) 2 (EPTB) + ( 13 ) and (cycloheptadienyl)Fe(CO) 2 (EPTB) + ( 14 ) (9.8 and 11.4 kcal mol -1 , respectively) and basal−basal phosphine exchange in (bicyclo[5.1.0]octadienyl)Fe(CO) 2 PPh 3 + ( 15 ) (13.3 kcal mol -1 ) 3 …”
Synopsis:Cations of 3-methylpentadienyl ligated to Fe(CO)3 + or Fe(CO)2PPh3 + were prepared and characterized, the latter by single-crystal Xray analysis; reaction of these cations with carbon and heteroatom nucleophiles gave either (diene)iron complexes or 4-substituted-3-methyl-2-cyclohexenones.
AbstractThe title cations (9 and 12) were prepared by dehydration of (3-methyl-2,4-pentadien-1-ol)Fe(CO)2L + complexes. The structure of the (CO)2PPh3-ligated 12 was determined by single-crystal X-ray analysis. Reaction of carbon and heteroatom nucleophiles to (3-methylpentadienyl)Fe(CO)3 + cations 9 and 12 proceeds either via attack at the dienyl terminus to give (3-methyl-1,3Z-diene)iron complexes or via attack at the internal carbon, followed by carbon monoxide insertion and reductive elimination to afford 3-methyl-4-substituted cyclohexenones. Cyclohexenone formation was found to be prevalent for addition of stabilized nucleophiles with strongly dissociated counterions to cation 9 (L = CO). Reaction of cation 9 with sodium bis[(−)-8-phenylmenthyl] malonate gave a single diastereomeric cyclohexenone.
“…The internal dienyl hydrogens H 2 and H 2 ‘ coalesce at −10 °C, corresponding to k c = 349 s -1 and Δ G ⧧ =12.8 kcal mol -1 . This activation energy is comparable with that found for apical−basal phosphite exchange in (cyclohexadienyl)Fe(CO) 2 (EPTB) + ( 13 ) and (cycloheptadienyl)Fe(CO) 2 (EPTB) + ( 14 ) (9.8 and 11.4 kcal mol -1 , respectively) and basal−basal phosphine exchange in (bicyclo[5.1.0]octadienyl)Fe(CO) 2 PPh 3 + ( 15 ) (13.3 kcal mol -1 ) 3 …”
Synopsis:Cations of 3-methylpentadienyl ligated to Fe(CO)3 + or Fe(CO)2PPh3 + were prepared and characterized, the latter by single-crystal Xray analysis; reaction of these cations with carbon and heteroatom nucleophiles gave either (diene)iron complexes or 4-substituted-3-methyl-2-cyclohexenones.
AbstractThe title cations (9 and 12) were prepared by dehydration of (3-methyl-2,4-pentadien-1-ol)Fe(CO)2L + complexes. The structure of the (CO)2PPh3-ligated 12 was determined by single-crystal X-ray analysis. Reaction of carbon and heteroatom nucleophiles to (3-methylpentadienyl)Fe(CO)3 + cations 9 and 12 proceeds either via attack at the dienyl terminus to give (3-methyl-1,3Z-diene)iron complexes or via attack at the internal carbon, followed by carbon monoxide insertion and reductive elimination to afford 3-methyl-4-substituted cyclohexenones. Cyclohexenone formation was found to be prevalent for addition of stabilized nucleophiles with strongly dissociated counterions to cation 9 (L = CO). Reaction of cation 9 with sodium bis[(−)-8-phenylmenthyl] malonate gave a single diastereomeric cyclohexenone.
“…During the cyclopropane ring opening, an empty p orbital develops that can interact with the adjacent metal–alkene complex, ultimately providing a π-allyl species that could be used in subsequent reactions (eq 2). Although there is extensive research involving cyclopropane ring opening, there have been only a few examples of reactions involving cyclopropanes on organometallic scaffolds. − In part this is due to the propensity of cyclopropane rings to react directly with a metal center. , …”
The
complexes TpW(NO)(PMe3)(L), where L = 2H-phenol, 2H-p-cresol, 2H-5,6,7,8-tetrahydro-2-naphthol, 2H-
N,N-dimethylanilinium were cyclopropanated
using Simmons–Smith conditions. Cyclopropanated derivatives
of 2H-N,N-dimethylanilinium were
selectively ring-opened with HOTf/MeCN to form allylic species, which
could be coupled with various nucleophiles. The nucleophilic addition
occurs anti to the metal fragment, as determined
by X-ray crystallography. Moreover, the cyclopropane ring opening
occurs regioselectively, owing to the stabilization of the allylic
cation by the metal fragment. The resulting ligands can, in some cases,
be removed from the metal by oxidative decomplexation using ceric
ammonium nitrate (CAN).
“…As we have previously reported,8b osmium‐catalyzed hydroxylation of 7 with excess NMO as a reoxidant gave a separable mixture of two tetraols (±)‐ 24 and (±)‐ 25 (Scheme ). The structures of 24 and 25 were tentatively assigned on the basis of their 1 H NMR spectral data (see below); these tentative assignments were eventually corroborated by single‐crystal X‐ray diffraction analysis (Figure 3 and Figure 4).…”
Section: Resultsmentioning
confidence: 70%
“…N ‐(Bicyclo[5.1.0]hepta‐3,5‐dien‐1‐yl)phthalimide (±)‐ 7 was prepared from cyclooctatetraene in five steps and in 62 % yield using a slight modification to the literature procedure (Scheme ) 8b. The use of 2,3‐dichloro‐5,6‐dicyanoquinone (DDQ) instead of ceric ammonium nitrate (CAN) in the oxidative decomplexation step was found to give superior yields.…”
A series of eight stereoisomeric N-(tetrahydroxy bicyclo-[5.1.0]oct-2S*-yl)phthalimides were prepared in one to four steps from N-(bicyclo[5.1.0]octa-3,5-dien-2-yl)phthalimide (±)-7, which is readily available from cyclooctatetraene (62 % yield). The structural assignments of the stereoisomers were established by 1 H NMR spectral data as well as X-ray crystal structures for certain members. The outcomes of several epoxydiol hydrolyses, particularly ring contraction and enlargement, are of note. The isomeric phthalimides as well as the free amines did not exhibit β-glucosidase inhibitory activity at a concentration of less than 100 μM.
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