Benzannelated annulenes. 6. Toward the understanding of benzannelated annulenes: synthesis and properties of [a]-ring monobenzannelated dihydropyrenes

Abstract

The benzannelated dihydropyrenes 3 and 4 were synthesized from l,3-bis(bromomethyl)naphthalene ( 16) and l,3-bis(bromomethyl)-2-methylnaphthalene (22) (the latter obtained in 18% yield in seven steps from 2,3-dimethylnaphthalene) in 7.4% and 4.8% overall yields, respectively, using Stevens or Wittig rearrangement-Hofmann elimination sequences on the dithiacyclophanes 13 and 14, followed by valence tautomerization of the resulting cyclophanedienes 11 and 12. The dihydrobenzopyrene 3 rapidly dehydrogenates to benzo[a]pyrene (21), whereas the dimethyl derivative 4 is relatively stable.

Synthesis and conformational studies of 9-methoxy[3.3]metacyclophanes and 9-methoxy[3]metacyclo[3](2,6)pyridinophane

“…This result is quite different from the result in which the coupling reaction of 1,3bis(bromomethyl)-2-methoxy-5-substituted benzenes and 2,6bis[2-isocyano-2-(tolylsulfonyl)-ethyl]-4-tert-butylanisole 2 under the same reaction conditions to predominantly afford syn-9, 18-dimethoxy-6-tert-butyl-15-substituted [3.3]MCP-2,11-diones. 41 Although the detailed reaction pathway of the formation of anti-3 is still not clear from the present results, one might propose the interaction between the non-bonding electron pairs of the oxygen atom of the methoxy group and the opposite aromatic π-electrons might be unfavorable for the formation of anti-9-methoxy [3.3]MCP-2,11-diones anti-3. However, the present steric repulsion of 9-methoxy group and the opposite benzene ring could be reduced by making the distance longer arising from H-π attracting interaction between the opposing 18-proton and the opposite benzene ring than that for anti-9,18-dimethoxy [3.3]MCP-2,11-diones anti-4 as shown in Fig.…”

“…E-mail: yamatot@cc.saga-u.ac.jp and a singlet for the internal methoxy group at an upfield shift δ = 3.33 ppm from anisole (δ = 3.75 ppm) due to the ring current of the opposing aromatic ring. [25][26][27][32][33][34][35][36][37][38][39][40][41][42] Similarly, the internal aromatic proton at 18-position was observed at higher field, δ 5.55 ppm compared to that of the 1a at δ 7.28 ppm. These observations strongly suggest that compound anti-3a adopts the anti-conformation.…”

“…Further, the aryl hydrogens at 5, 7-positions can clearly be seen to be shielded at δ 6.48 ppm by the adjacent pyridine ring, a common consequence of a face-to-face benzene ring. [32][33][34][35][36][37][38][39][40][41][42] Also the tert-butyl protons was observed at higher field, δ 1.02 ppm compared to that of the anti-6 at δ 1.32 ppm due to the strong shielding effect of the ben zene ring.…”

Synthesis and conformational studies of 9-substituted [3.3]metacyclophane-2,11-diones and conversion to the corresponding [3.3]metacyclophanes

“…Furthermore, the aryl hydrogens at 5,7-positions can clearly be seen to be shielded at 6.61 ppm by the adjacent ring, a common consequence of a face-to-face benzene ring. [33][34][35][36][37][38][39][40][41][42][43] Also the tert-butyl protons was observed at higher 0.89 ppm compared to that of the anti-4d at 1.34 ppm due to the strong shielding effect of the benzene ring. These observations strongly suggest that compound syn-4d adopts syn-conformation.…”

Synthesis and Conformational Studies of 2,11-Dithia[3]Metacyclo-[3](1,3)Pyrenophanes: The Ring Current Interactions Derived from Pyrene Ring

“…These results indicate that the dithia [3]metacyclo [3] (1,3)pyrenophanes 3 are highly flexible molecules like dithia [3.3]MCPs. 17,25,26 In order to obtain more detail informations concerning on the conformations of 2, ll-dithia [3]metacyclo [3](1 ,3) pyrenophanes 3, we have prepared 9-methoxy derivative 7 in 52% yield by coupling the 1,3-bis(bromomethyl)-7-tertbutylpyrene 1 with 2,6-bis(sulfanylmethyl)-4-methylanisole 6 under highly diluted conditions in 10% ethanolic potassium hydroxide in the presence of a small amount of sodium borohydride as shown in Scheme 2.…”