Synthesis and rearrangement reactions of 1,4-dihydrospiro[1,4-methanonaphthalene-9,1′-cyclopropane] derivatives
Graphical abstract
Introduction
Among the molecular rearrangements in organic chemistry, Wagner-Meerwein rearrangement takes an important place [1]. This rearrangement can be seen in the form of single or sequential rearrangements, and they can lead to the formation of important structures. Transformation of cyclopropylmethanols and their derivatives into homoallylic derivatives is a useful reaction [2].
In compounds 1 and 2, a cyclopropane ring is combined with benzonorbornadiene and benzobarrelene giving skeletal rearrangements [1](b), [3] in ionic medium. When R was CH2OH in 1 and 2, we observed that their reactions with SOCl2 gave sequential rearrangements starting with cyclopropane rings [4]. Furthermore, we observed that the reaction of 2 (R = COOMe) with Br2 gave products derived from skeletal rearrangements (Fig. 1) [5]. Starting from the compound 1 where R (COOMe) is exo-configuration, the same route was used in the synthesis of exo-9-ethyl-1,4-dihydro-1,4-methanonaphthalene [4](b), [6].
To form a substituted cyclohexene derivative, Diels–Alder reaction is realized stereospecifically between a conjugated diene and a dienophile. The Diels–Alder reactions are particularly used in synthetic organic chemistry, and their reaction product is called adduct [7]. Adducts 4 were synthesized from the reactions of compound 3 with different dienophiles, and their rearrangement reactions were investigated [8]. Recently, we reported that rearrangements of adduct 5 and adduct of compound 6 with dimethyl 1,2,4,5-tetrazine-3,6-dicarboxylate rearranged without SOCl2 (Fig. 1) [9]. These rearrangements are new and also include cleavages of carbon-nitrogen or carbon-carbon bonds in them [9].
Benzyne is used in the Diels-Alder reactions as dienophile [10]. It is used in the synthesis of cyclopropanetad benzonorbornadiene and benzobarrelene derivatives 1 and 2 as dienophile [1](b), [4]. Adducts of compound 3 and its derivatives with benzyne are important because interesting rearrangements may occur in them. Therefore, adducts of 3 and its ester derivatives with benzyne were synthesized, and investigated their rearrangements reactions.
Section snippets
Results and discussion
Spiro alcohol 3 and its ester derivatives 7–9 were synthesized by a known method [9a]. Benzyne is a good dienophile and is formed in the reaction medium as an intermediate product. The reaction medium is acidic because benzenediazonium 2-carboxylate hydrochloride salt (BDCHCl) was used as the source of the benzyne [10,11]. Spiro alcohol 3 was not used because it might be unstable in the related reaction condition.
The reaction of ester 7 whose R group is Ac with BDCHCl (10) was performed. The 1H
Conclusion
Reactions of esters 7–9 with benzyne were performed with the same conditions (by reflux of a mixture of each ester, BDHCl and 1,2-dichloroethane). From adducts formed in the reactions, compounds 11–14 were isolated in the corresponding reaction mixtures. It was observed that the size of ester groups in adducts is effective in their isolations.
As shown in Fig. 5, we can think of compounds such as 13 including three units as cyclopropyl methanol (A), norbornadiene or norbornene (B) and benzene
General experimental procedures
Solvents were purified and dried by standard methods. Values as well as measurements of M.p. of all compounds, IR spectra, 1H and 13C NMR spectra, and chemical shift values were obtained, and elemental analyses, was performed as described previously [9]. PLC is preparative thin-layer chromatography: 1 mm of silica gel 60 PF (Merck, Darmstadt, Germany) on glass plates. HRMS were recorded by LC-MS-TOF electrospray ionization (1200/6210, Agilent).
Crystallographic data
For the crystal structure determination, single-crystal compounds 13, 15 and 31 were used for data collection on a four-circle Rigaku R-AXIS RAPID-S diffractometer (equipped with a two-dimensional area IP detector). Graphite-monochromated Mo-Kα radiation (λ = 0.71073 Å) and oscillation scans technique with Δw = 5° for one image were used for data collection. The lattice parameters were determined by the least-squares methods on the basis of all reflections with F2 > 2σ(F2). Integration of the
Acknowledgments
This study was financed by TÜBITAK - The Scientific and Technological Research Council of Turkey (Project No: 109T403) and realized in Atatürk University, Faculty of Science, Department of Chemistry. We are grateful to both institutes for their supports.
References (18)
- et al.
J. Org. Chem.
(2009) - et al.
Tetrahedron
(2016)et al.Tetrahedron
(2017) - et al.
J. Am. Chem. Soc.
(1983)Chem. Rev.
(1989) SHELXS97 and SHELXL97
(1997)- et al.
Principle of Organic Synthesis
(1993)Top. Curr. Chem.
(1984) - et al.
J. Am. Chem. Soc.
(1968)et al.J. Org. Chem.
(1981) - et al.
J. Org. Chem.
(1972)et al.Tetrahedron
(1994)et al.Rev. Roum. Chim.
(2006)et al.Rev. Chim.
(2008) Tetrahedron
(2000)et al.Helv. Chim. Acta
(2003)et al.Turk. J. Chem.
(2004)- et al.
Tetrahedron
(1997)