Synthesis of 7-azabicyclo[4.3.1]decane ring systems from tricarbonyl(tropone)iron via intramolecular Heck reactions

• Aaron H. Shoemaker,
• Elizabeth A. Foker,
• Elena P. Uttaro,
• Sarah K. Beitel and
• Daniel R. Griffith

Beilstein J. Org. Chem. 2023, 19, 1615–1619, doi:10.3762/bjoc.19.118

• accessed from tropone (via its η4-diene complex with Fe(CO)3) in a short sequence of steps: 1) nucleophilic amine addition and subsequent Boc-protection, 2) photochemical demetallation of the iron complex, and 3) an intramolecular Heck reaction. Minor modifications to the protocol enabled access to the

• related 2-azabicyclo[4.4.1]undecane system, albeit in lower yield. Keywords: alkaloids; azabicycles; Heck reaction; iron complex; tropone; Introduction Azapolycycles are embedded within numerous biologically active alkaloids [1] and pharmaceuticals [2]. As such, novel approaches to the synthesis of

• these scaffolds, even though they are found within a number of biologically active alkaloids. We recently demonstrated that the readily available, bench-stable tricarbonyl(tropone)iron complex [4] (1, Scheme 1) could serve as a precursor to the previously unreported 2-azatricyclo[4.3.2.04,9]undecane

Group 13 exchange and transborylation in catalysis

• Dominic R. Willcox and
• Stephen P. Thomas

Beilstein J. Org. Chem. 2023, 19, 325–348, doi:10.3762/bjoc.19.28

• and HBcat (Scheme 27) [122]. The precatalyst ([Fe(CH3CN)6][cis-Fe(CO)4(InCl3)2]) was activated in situ with HBpin to give ClBpin and HInCl2 107 by In‒Cl/B‒H exchange. The indium hydride 107 underwent hydroelementation of an iron-coordinated nitrile 108, to give an indylimine iron complex 109, which

• after In‒N/B‒H exchange with HBpin gave a borylimine iron complex 110. A second hydroelementation and In‒N/B‒H exchange gave the bisborylamine 113 and regenerated the HInCl2 107 co-catalyst (Scheme 27). Conclusion Increasing concerns over the sustainability and toxicity of many transition-metal

Recent developments and trends in the iron- and cobalt-catalyzed Sonogashira reactions

• Surendran Amrutha,
• Sankaran Radhika and
• Gopinathan Anilkumar

Beilstein J. Org. Chem. 2022, 18, 262–285, doi:10.3762/bjoc.18.31

• iron complex B is formed by the oxidative addition of the iron catalyst to the pyridine derivative. Intermediate Fe species were obtained by transmetallation and finally a new carbon–carbon bond is formed by reductive elimination (Scheme 19). This method provided access to a diverse range of 7

Iron-catalyzed domino coupling reactions of π-systems

• Austin Pounder and
• William Tam

Beilstein J. Org. Chem. 2021, 17, 2848–2893, doi:10.3762/bjoc.17.196

• bond of the aromatic ring in 47. Capturing of the iron complex by the Grignard reagent 2, followed by reductive elimination would deliver the observed product 40. Alternatively, the iron species 45 may undergo direct anti-attack by the Grignard reagent (path ii) [76]. One final possibility is the

Synthetic approaches to bowl-shaped π-conjugated sumanene and its congeners

• Shakeel Alvi and
• Rashid Ali

Beilstein J. Org. Chem. 2020, 16, 2212–2259, doi:10.3762/bjoc.16.186

Organometallic vs organic photoredox catalysts for photocuring reactions in the visible region

• Aude-Héloise Bonardi,
• Frédéric Dumur,
• Guillaume Noirbent,
• Jacques Lalevée and
• Didier Gigmes

Beilstein J. Org. Chem. 2018, 14, 3025–3046, doi:10.3762/bjoc.14.282

• charge-transfer transition [33]. An example of an iron complex photoredox catalyst FeC1 is given in Scheme 2 and the associated photochemical properties gathered in Table 5. A synthesis of this complex is detailed in reference [66]. This iron complex with tetradentate monophenolate ligands has raised

One hundred years of benzotropone chemistry

• Arif Dastan,
• Haydar Kilic and
• Nurullah Saracoglu

Beilstein J. Org. Chem. 2018, 14, 1120–1180, doi:10.3762/bjoc.14.98

• the thermal and electron impact-induced decarbonylation reaction of 12 (Scheme 36) [131]. Tajiri’s group reported the resolution and determination of the kinetic parameters of the optically active 2,3-benzotropone(tricarbonyl)iron complex 221 using high-performance liquid chromatography (HPLC) and

Transition-metal-catalyzed synthesis of phenols and aryl thiols

• Yajun Liu,
• Shasha Liu and
• Yan Xiao

Beilstein J. Org. Chem. 2017, 13, 589–611, doi:10.3762/bjoc.13.58

• they used a stoichiometric amount of reactive iron complex [Fe(II)(BPMEN)(CH3CN)2](ClO4)2 to achieve ortho-hydroxylation of benzoic acid in the presence of H2O2, affording salicylic acid in low yields [52]. In the past decade, the selectivity and yield of C–H hydroxylation of arenes were highly

Catalytic Wittig and aza-Wittig reactions

• Zhiqi Lao and
• Patrick H. Toy

Beilstein J. Org. Chem. 2016, 12, 2577–2587, doi:10.3762/bjoc.12.253

• formation of the required ylide intermediate, a base is not necessary, but the authors reported that when it was omitted from a control reaction, no reaction occurred. Finally, Bernd Plietker and co-workers have very recently reported the use of iron complex 38 as a catalyst for phosphine oxide reduction

Creating molecular macrocycles for anion recognition

• Amar H. Flood

Beilstein J. Org. Chem. 2016, 12, 611–627, doi:10.3762/bjoc.12.60

• indicated that triazoles are sterically small. In the iron complex, we saw the ferrous ion’s preference for triazole change to a water molecule when oxidized up to the harder ferric ion. This process did not occur with the terpyridine control complex. Thus, we reasoned water could easily slip past the

Iron complexes of tetramine ligands catalyse allylic hydroxyamination via a nitroso–ene mechanism

• David Porter,
• Belinda M.-L. Poon and
• Peter J. Rutledge

Beilstein J. Org. Chem. 2015, 11, 2549–2556, doi:10.3762/bjoc.11.275

• cyclohexene (7) [45][46][47], we wished to explore potential C–N bond formation at this position using iron catalysis. Combining cyclohexene (7, in excess) with N-Boc-hydroxylamine (8) as the nitrogen source and the iron complex FeTPA (4) or FeBPMEN (5) afforded a mixture of products: the allylic

• conditions), the solvent was subjected to three freeze–thaw degassing cycles immediately before use. Stock solutions of iron complex (22.6 mmol L−1) and BocNHOH (8, 70 mmol L−1) in degassed acetonitrile were prepared under an atmosphere of argon. Acetonitrile (8.0 mL) was stirred under the required

• environment (argon or air) while iron complex stock solution (0.3 mL, 6.8 μmol) and cyclohexene (0.7 mL, 6.9 mmol) were added. Using a syringe pump, the BocNHOH stock solution (1.0 mL, 70 μmol) was added to the reaction mixture over 30 min. The reaction was stirred for 18 h after which time the solvent was

Selected synthetic strategies to cyclophanes

• Sambasivarao Kotha,
• Mukesh E. Shirbhate and
• Gopalkrushna T. Waghule

Beilstein J. Org. Chem. 2015, 11, 1274–1331, doi:10.3762/bjoc.11.142

• the pyridine derivative 220 with an excess amount of the 5-hexenylmagnesium bromide in the presence of a catalytic amount of iron complex 18 as the precatalyst provides the dialkylation product 221 (75%). The treatment of the hydrochloride solution of 221 with Ru catalyst 17 in a dilute CH2Cl2

Electrochemical oxidation of cholesterol

• Jacek W. Morzycki and
• Andrzej Sobkowiak

Beilstein J. Org. Chem. 2015, 11, 392–402, doi:10.3762/bjoc.11.45

• ]. In Gif systems pyridine is not only used as a solvent but it also acts as a ligand on the iron complex [28]. Different Fe(II) or Fe(III) picolinate (PA) and dipicolinate (DPA) complexes as catalysts of oxygenation reactions have been studied by the Sawyer [29][30][31], Barton [31][32], and Kotani

• %), along with the 7-oxo product 9a (15–19%). In addition to these products, epoxide 10a (1.5–3%) was also formed under constant current conditions (Scheme 3). Irrespective of the iron complex used, the reactions afforded the 7α-hydroxylated product 7a in a large excess. The authors postulated the formation

Recent applications of the divinylcyclopropane–cycloheptadiene rearrangement in organic synthesis

• Sebastian Krüger and
• Tanja Gaich

Beilstein J. Org. Chem. 2014, 10, 163–193, doi:10.3762/bjoc.10.14

• vinyl bromide 227 (see Scheme 27) formation of the corresponding Grignard species was acomplished, followed by addition to organoiron complex 228 to give (pentenediyl)iron complex 229. Oxidation led to the formation of the desired divinylcyclopropane, followed by reduction of the ester to the desired

Formal synthesis of (−)-agelastatin A: an iron(II)-mediated cyclization strategy

• Daisuke Shigeoka,
• Takuma Kamon and
• Takehiko Yoshimitsu

Beilstein J. Org. Chem. 2013, 9, 860–865, doi:10.3762/bjoc.9.99

• deserve discussion (Scheme 4). We hypothesize that cyclized material 5a/5b, reduced material 9, and enone 10 are generated from an N–iron complex (i) that has free-radical character, as previously proposed in the catalytic cyclization of azidoformates [30][38][39][40]. The contrasting yields obtained from

• reactive FeX2 through capture with the polar amide functionality of 8. It is speculated that product 9 may be produced by trapping N–iron complex (i) with another FeX2 (i→vii→9), whereas enone 10 is likely to be generated via intramolecular allylic hydrogen abstraction followed by halogen transfer to

• , and combined the resultant radicals (hydrogen atom abstraction/radical rebound pathway) to provide amides [43][44]. The involvement of such an iron complex (shown in brackets in Scheme 4) that features radical/metal–nitrenoid properties can be considered in our reactions. A recent study by Betley and