Synthesis of Substituted Sumanenes by Aromatic Electrophilic Substitution Reactions

Abstract

Electrophilic substitution reactions of sumanene were studied. Mono-, di-, and trisubstituted sumanenes were selectively prepared with the separation of all regioisomers. The regioselectivity was predicted well by the HOMO density values determined by DFT calculations.The regioselective synthesis of aromatic compounds, including sumanene derivatives, is very important in order to explore their physical properties.1 For example, two sumanene derivatives trisubstituted at the benzene rings, C 3 symmetric and unsymmetrical, are possible if ortho-substituted derivatives are excluded. Previously, we developed the functionalization of C 3 symmetric derivatives from precursor A (Scheme 1).2 However, direct preparation of both isomers from sumanene (1) 3 is also beneficial if these isomers can be easily separated or one isomer can be selectively obtained. A more complicated situation is encountered in the case of disubstituted sumanene synthesis; three possible isomers may be produced (Table 1).Electrophilic aromatic substitution (S E Ar) is one of the most reliable methods for the direct functionalization of aromatic compounds. However, due to the lack of regioselectivity and the difficulty in separation of the regioisomers, the S E Ar route has rarely been applied to sumanene derivatization. 4 The purpose of this study involves the development of regioselective electrophilic substitution reactions of sumanene, and prediction of their regioselectivity by DFT calculations.Selective syntheses of monosubstituted sumanenes were first investigated as summarized in Scheme 2.5 Iodosumanene (2) was selectively prepared in 75% yield by AuCl 3 -catalyzed iodination 6 with N-iodosuccinimide (NIS) with recovery of 1. Nitrosumanene (3) was obtained in 65% yield by nitration using trifluoroacetyl nitrate, generated in situ from trifluoroacetic anhydride and concd nitric acid.7 1 was completely consumed and dinitrosumanenes were not formed. However, some amount of degradation was observed due to the harsh conditions. Formylation was achieved using triflic anhydride and DMF 8 under microwave-assisted heating conditions to afford formylsumanene (4) in 60% yield. Because of the low reactivity of the reagent, high temperature (130°C) was required to complete the reaction. Although diformylsumanenes were also formed in 20% yield with 4, these compounds were easily separated from 4 by preparative thin layer chromatography (PTLC). Acetylation was achieved by adopting similar conditions as the formylation in the presence of DMA to afford acetylsumanene (5) in 64% yield and diacetylsumanenes in 10% yield. Benzoylsumanene (6) was also prepared in 68% yield using triflic acid and PhCOCl with complete consumption of 1.9 They were easily purified by PTLC as well.The thus-employed reaction conditions were further applied to the syntheses of disubstituted sumanenes (Table 1).10 Preparation of diiodosumanenes 7, dinitrosumanenes 8, diformylsumanenes 9, diacetylsumanenes 10, and dibenzoylsumanenes 11 were achieved by increasing the amount of reagent...

Correlation between bowl-inversion energy and bowl depth in substituted sumanenes

“…We therefore prepared trideuterosumanene with high D/H ratio ( > 99 %) by deuteration of tris(trimethylsilyl)sumanene (5) [10] (Scheme 1). Trideuterated iodosumanene (2b), sumanenecarbaldehyde (2c), and nitrosumanene (2d) were prepared from trideuterosumanene by following our reported methods [11].…”

“…Monosubstituted sumanene derivatives (R = I, CHO, NO 2 ) were prepared according to procedure given in reference [11]. All 2D-EXSY spectra were recorded according to procedure given in reference [7a].…”

Columnar/herringbone dual crystal packing of pyrenylsumanene and its photophysical properties

“…The preparation of iodosumanene was improved by using a catalytic amount of scandium (III)triflate (Sc(OTf) 3 ) with 6,6’-diiodo-2,2’-dimethoxy-1,1’-binaphthol (DIH) [23] compared to the previously reported system of AuCl 3 and N -iodosuccinimide [8], resulting in an 80% yield.…”

Synthesis, Structures, and Physical Properties of Aromatic Molecular-Bowl Hydrocarbons

“…Trisubstituted sumanenes, such as C 3 symmetric triformylsumanene and its derivatives, were synthesized regioselectively by using suitable reaction intermediates syn-tri(norborneno)benzenes (cf. Scheme 36) [144].…”