Transition-metal-catalyzed domino reactions of strained bicyclic alkenes

• Austin Pounder,
• Eric Neufeld,
• Peter Myler and
• William Tam

Beilstein J. Org. Chem. 2023, 19, 487–540, doi:10.3762/bjoc.19.38

• and Renaud expanded the scope of the photoredox/Ni dual-catalyzed coupling of alkyl nucleophiles 36 with heterobicyclic alkenes 30 to include α-amino radicals (Scheme 7) [40]. The authors noted the electron-rich oxabenzonorbornadiene derivatives provided the corresponding ring-opened adducts in good

• yields (63–68% yield) while those bearing EWG led to poor product formation. Unlike Gutierrez and Molander’s work (Scheme 6) [39], it was found mono- and disubstituted bridgeheads affected the efficacy of the reaction with the demethylated bridgehead oxabenzonorbornadiene only delivering the product in a

• 20% yield. Although yields were slightly diminished, unsymmetrical bridgehead-monosubstituted oxabenzonorbornadiene led solely to the 1,2,4-trisubstituted regioisomer (Scheme 7), similar to that observed by Gutierrez and Molander [39]. Selected substituents on the aniline motif were found to hamper

Iridium-catalyzed hydroacylation reactions of C1-substituted oxabenzonorbornadienes with salicylaldehyde: an experimental and computational study

• Angel Ho,
• Austin Pounder,
• Krish Valluru,
• Leanne D. Chen and
• William Tam

Beilstein J. Org. Chem. 2022, 18, 251–261, doi:10.3762/bjoc.18.30

• attractive. Transition-metal-catalyzed reactions of strained bicyclic derivatives have been an intense area of research in the last 20 years (Scheme 1) [14][15][16][17]. Of particular interest is oxabenzonorbornadiene (OBD, 1), as it bears multiple points of reactivity that allow for diverse

• reported metal-catalyzed reactions of heterobicyclic alkenes and applications towards the synthesis of biologically active compounds (top). Representative examples of regioselectivity in different metal-catalyzed ring-opening reactions of C1-substituted oxabenzonorbornadiene derivatives (bottom left

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

• ]. Transformation of adduct 31 to 11 starts with the synthesis of the stable cyclopropanoid tricyclic 32 from the reaction of the 7-oxabenzonorbornadiene 31 with dichlorocarbene, generated by the phase-transfer method. The thermolysis of dichloride 32 in nitrobenzene at 165 °C resulted in the formation of ring

Palladium-catalyzed ring-opening reactions of cyclopropanated 7-oxabenzonorbornadiene with alcohols

• Katrina Tait,
• Oday Alrifai,
• Rebecca Boutin,
• Jamie Haner and
• William Tam

Beilstein J. Org. Chem. 2016, 12, 2189–2196, doi:10.3762/bjoc.12.209

• cyclopropanated 7-oxabenzonorbornadiene derivatives using alcohol nucleophiles were investigated. The optimal conditions were found to be 10 mol % PdCl2(CH3CN)2 in methanol, offering yields up to 92%. The reaction was successful using primary, secondary and tertiary alcohol nucleophiles and was compatible with a

• variety of substituents on cyclopropanated oxabenzonorbornadiene. With unsymmetrical C1-substituted cyclopropanated 7-oxabenzonorbornadienes, the regioselectivity of the reaction was excellent, forming only one regioisomer in all cases. Keywords: alcohol nucleophiles; C1 substitution; cyclopropanated

• oxabenzonorbornadiene; palladium catalysis; ring-opening reactions; Introduction Heterobicyclic alkenes undergo important chemical transformations to provide highly substituted cyclic and acyclic systems [1][2]. Oxabicyclic alkene 1 specifically can undergo a variety of chemical transformations to generate highly

Regioselective palladium-catalyzed ring-opening reactions of C1-substituted oxabicyclo[2,2,1]hepta-2,5-diene-2,3-dicarboxylates

• Michael Edmunds,
• Mohammed Abdul Raheem,
• Rebecca Boutin,
• Katrina Tait and
• William Tam

Beilstein J. Org. Chem. 2016, 12, 239–244, doi:10.3762/bjoc.12.25

• ; oxabenzonorbornadiene; palladium catalysis; regioselectivity; ring-opening reactions; Introduction Palladium-catalyzed ring-opening reactions of 7-oxanorbornadiene with aryl iodides produce unsymmetrical, highly-substituted biphenyl derivatives making this reaction a very useful tool in organic synthesis [1][2][3][4

• materials [8]. Although there are several examples of palladium-catalyzed ring-opening reactions of oxabenzonorbornadiene (Scheme 1), there is relatively little literature regarding reactions of non-aromatic 7-oxanorbornadiene systems [9][10][11][12][13]. To our knowledge, there has only been one example of

• reaction of oxabenzonorbornadiene with aryl iodides (Scheme 4) [15]. We found that the electron-withdrawing methoxycarbonyl substituent on the aryl iodide or bridgehead carbon lowered the yield in all cases and gave aromatized products, while the electron-donating ethyl group on the aryl iodide or

N–O Cleavage reactions of heterobicycloalkene-fused 2-isoxazolines

• Jaipal R. Nagireddy,
• Geoffrey K. Tranmer,
• Emily Carlson and
• William Tam

Beilstein J. Org. Chem. 2014, 10, 2200–2205, doi:10.3762/bjoc.10.227

• isoxazolines. Effects of arene substitution on Raney Ni/AlCl3-mediated cleavage of symmetrical 7-oxabenzonorbornadiene-fused 3-methyl-2-isoxazolines. Effects of bridgehead substitution on Raney Ni/AlCl3 mediated cleavage of 7-oxabenzonorbornadiene-fused 3-methyl-2-isoxazolines. Supporting Information

Iridium-catalyzed asymmetric ring-opening reactions of oxabicyclic alkenes with secondary amine nucleophiles

• Dingqiao Yang,
• Ping Hu,
• Yuhua Long,
• Yujuan Wu,
• Heping Zeng,
• Hui Wang and
• Xiongjun Zuo

Beilstein J. Org. Chem. 2009, 5, No. 53, doi:10.3762/bjoc.5.53

• -catalyzed asymmetric ring-opening of oxabenzonorbornadiene with a wide range of nucleophiles including thiols [10], phenols [11], organoboronic acids [12][13], dialkylzincs [14][15], carboxylates [16], sulfur nucleophiles [17], and various amines [18][19]. In addition to rhodium catalysts, other transition

• . Using (S)-p-Tol-BINAP as our standard ligand, we next investigated the effect of different solvents on reactivity and enantioselectivity (Table 1). Among the solvents examined for asymmetric ring-opening of oxabenzonorbornadiene 1a, THF was found to be the best in terms of yield and enantioselectivity

• above findings, we decided to use the following reaction condition as a standard to run the ARO reactions, which consisted of 2.5 mol % [Ir(COD)Cl]2, 5 mol % (S)-p-Tol-BINAP, and 3.0 equiv of substituted N-alkylaniline in THF at 80 °C. The results of the ARO of oxabenzonorbornadiene 1a are shown in