Thiourea-catalyzed Diels–Alder reaction of a naphthoquinone monoketal dienophile

• Carsten S. Kramer and
• Stefan Bräse

Beilstein J. Org. Chem. 2013, 9, 1414–1418, doi:10.3762/bjoc.9.158

• tricycle of beticolin 0 (1) and is also a valuable model substrate for the total synthesis of related natural products. Keywords: beticolin 0; Diels–Alder reaction; natural product; organocatalysis; thiourea catalysis; total synthesis; Introduction In the past few years, many different types of

• ][8]. In our recent studies towards a synthetic access to the natural product beticolin 0 (1) [9] (Scheme 1), we have found that naphthoquinone monoketals are suitable building blocks for our designed synthesis [9]. In our retrosynthetic approach, the naphthoquinone monoketal dienophile 3 was found to

• undergo cycloaddition with diene 4 to tricycle 2, which represents the ABC-ring system of beticolin 0 (1) and other beticolins [10]. We found that dienophile 3 and diene 4 can undergo a cycloaddition by applying either thermal conditions or microwave irradiation to these both compounds (Table 1) [9