Abstract
Two alternative procedures, both starting from easily accessible tetramethylanthracenes and employing the Diels-Alder addition as the key reaction step(s), have been examined in the synthesis of the title compounds.
Key words
carboxylic acids - Diels-Alder reactions - oxidations - triptycenes - arynes
References
1a Holý P.
Závada J.
Císařová I.
Podlaha J.
Angew. Chem. Int. Ed.
1999,
38:
381
1b Holý P.
Sehnal P.
Tichý M.
Závada J.
Císařová I.
Tetrahedron: Asymmetry
2003,
14:
245
1c Holý P.
Kováč M.
Tichý M.
Závada J.
Buděšínský M.
Císařová I.
Tetrahedron: Asymmetry
2005,
16:
2031
1d Holý P.
Havlík M.
Tichý M.
Závada J.
Císařová I.
Collect. Czech. Chem. Commun.
2006,
71:
139
2 Rybáček J.; Rybáčková, M.; Høj, M.; Holý, P.; Bělohradský, M.; Kilså, K.; Nielsen, M. B., manuscript in preparation.
3 Rybáčková M.
Bělohradský M.
Holý P.
Pohl R.
Závada J.
Synthesis
2006,
2039
4
6a : 1 H NMR (400 MHz, CDCl3 ): δ = 1.84 (s, 6 H), 2.35 (s, 6 H), 4.77 (s, 2 H), 6.98 (m, 2 H), 7.29 (m, 2 H), 7.42 (s, 2 H), 7.50 (s, 2 H). 6b : 1 H NMR (400 MHz, CDCl3 ): δ = 1.83 (s, 6 H), 2.16 (s, 6 H), 2.34 (s, 6 H), 4.70 (s, 2 H), 7.10 (s, 2 H), 7.40 (s, 2 H), 7.46 (s, 2 H).
5 Similar problems with regioselectivity are common in aryne addition to anthracenes, cf. ref 6. Steric hindrance to aryne approach due to methyls may account well for the different outcomes obtained with anthracenes 1 and 4 in Scheme
[1
6 Klanderman BH.
Criswell TR.
J. Org. Chem.
1969,
34:
3426
7a Butler DN.
Snow RA.
Can. J. Chem.
1975,
53:
256
7b Ihmels H.
Schneider M.
Waidelich M.
Org. Lett.
2002,
4:
3247
8 Hart H.
Bashir-Hashemi A.
Luo J.
Meador MA.
Tetrahedron
1986,
42:
1641
9 Chan T.-L.
Mak TCW.
Poon C.-D.
Wong HNC.
Jia JH.
Wang LL.
Tetrahedron
1986,
42:
655.
10 Hinshaw JC.
Org. Prep. Proced. Int.
1972,
4:
211
11 Wilcox CF.
Farley EN.
J. Am. Chem. Soc.
1984,
106:
7195
12 Baker BR.
Schaub RE.
Joseph JP.
McEvoy FJ.
Williams JH.
J. Org. Chem.
1952,
17:
149
13 Skvarchenko VR.
Shil’nikova AG.
Zakharova G.
Levina RY.
Zh. Org. Khim.
1970,
6:
174 ; Chem. Abstr. 1970, 73, 3692
