Diels-Alder reactions using 4,7-dioxygenated indanones as dienophiles for regioselective construction of oxygenated 2,3-dihydrobenz[f]indenone skeleton

Abstract

Regioselective construction of 4,8,9-trioxygenated 2,3-dihydrobenz[f]indenones, key intermediates for the synthesis of kinamycin antibiotics, was achieved via Diels-Alder reactions (DAR) using 4,7-dioxygenated indanone-type compounds as dienophiles. Reaction of indanetrione with 1-methoxybutadiene gave a 1 : 1 mixture of undesired 4,5,9-trioxygenated 2,3-dihydrobenz [f]indenone and [4.4.3]propellane. The addition of Lewis acid did not affect the product ratio, whereas the use of the 6-bromoindanetrione exclusively afforded the latter propellane. On the other hand, DAR of benzyne derived from bromoindan and furan gave 5,8-epoxy-2,3-dihydrobenz[f]indene, which was subjected to acid-induced ring opening to give 2,3-dihydrobenz[f]indenone with undesired 4,5,9-trioxy functions.

Synthesis and Acid Catalyzed Rearrangement of Cage Propellanes

“…For this purpose, the indanone 15 was treated with NaBH 4 in methanol at 0 °C to provide the hydroxy compound 27 in 92% yield. Oxidation of the dimethoxy indane derivatives 15 and 27 in the presence of CAN at 0 °C in CH 3 CN/H 2 O delivered quinones 24 and 28 which acts as suitable dienophiles for DA reaction. Later, the DA precursors 24 14c and 28 were subjected to [4+2] cycloaddition sequence with freshly prepared cyclopentadiene ( 25 ) in MeOH to generate the DA adducts 26 and 29 in 79% to 84% yields.…”

Synthesis of 1-indanones with a broad range of biological activity

“…They were used in the key step of the synthesis of kinamycin 9 derivatives, which exhibited a strong cytotoxic and anticancer activity (Scheme 4) [15]. …”

A new approach towards synthesis of benzo[b]fluorene core

“…Another approach by Mal et al was based on ring contraction via the benzil-benzilic acid rearrangement of benzo[a]anthracene-5,6-diones [16]. Other noteworthy approaches are those utilizing [4+2] cycloadditions [17,18], other cycloadditions [17,19,20], and oxidative free radical cyclizations [21]. Birman and co-workers achieved the rapid ring construction of benzo[b]fluorenones via reaction of 1-indanone dianions with phthalate diesters.…”