1,4-Dipole-metalated quinone strategy to (.+-.)-4-demethoxydaunomycinone and (.+-.)-daunomycinone. Annelation of benzocyclobutenedione monoketals with lithioquinone bisketals

Abstract

882 cm'1 (m); UV 268 nm (e 9.6 X 103); mass spectrum, m/z = 148.0887 (M+, caled for C10H12O 148.0889).3-(3-Butenyl)cyclopent-2-enone (32). Following the procedure described above for the preparation of 11, the alcohol obtained from 3-butenylmagnesium bromide and cyclopent-2-enone (5.0 g, 61 mmol), after treatment with acidic Cr03, gave 32 (1.403 g, 17% overall), bp 110-115 °C (10 mm); further purification was achieved by preparative VPC on column D (175 °C): NMR (60 MHz) 6.13-5.47 (m, 1 H), 5.83 (dd, J = 1,1 Hz, 1 H), 5.22-4.8 (m, 2 ), 2.72-2.10 (m, 8 H); IR 3070 (w), 2955 (m), 1715 (s), 1672 (w), 1643 (m), 1617 (s), 1435 (m), 981 (m), 910 cm"1 (m); mass spectrum, m/z 136.0887 (M+, caled for C9H120 136.0887).Photolysis of 32. A solution of 32 (176 mg) in CeH6 (67 mL) was irradiated at 25 °C through an uranium glass filter for 10 days.VPC analysis on column G (178 °C) indicated two components and a considerable amount (~40%) of 32 remaining. After preparative VPC, a NMR spectrum of the first component indicated it was a mixture. Further separation was achieved on column H (150 °C); the first eluted component was identified as 14b: NMR (220 MHz) 2.

Protection and polymerization of functional monomers. 15. Anionic living polymerizations of 2-(3-vinylphenyl)-1,3-dioxolane and related monomers

“…Hz, CH2=), 5.50 (1 H, s, CHO), 3.65-3.42 (4 H, m, OCH2), 1.66-1.27 (8 H, m, CH2CH2), 0.9 (6 H, m, CH3); 23-MHz 13C NMR (CDC13) 13.9 (CH3), 19.5 (CH2CH2CH2CH3), 32.0 (CH2CH2-CH2CH3), 65.1 (OCH2), 101.4 (CHO), 113.9 (CH2=), 126.0,126.9…”

2‐Hydroxybenzocyclobutenone Ethylene Dithioacetals as Precursors of Highly Substituted 1,4‐Dihydronaphthalenes

“…The readily available benzocyclobutenedione monothioketal 5 [7] can be smoothly reduced to alcohol 6 by DIBAL. After work-up 6 is obtained in 77 % yield, but within minutes at room temperature it rearranges to aldehyde 7 by electrocyclic ring-opening and a subsequent [1,5] hydrogen shift (Scheme 2).…”

Recent chemistry of benzocyclobutenes

“…intermediate 244, suitable for further elaboration (Scheme 137). 151 A potential anthracycline derivative 247 has been prepared from the benzocyclobutenone 245 and the quinone acetal 246 as starting materials (Scheme 138). 152 Several conjugated semiquinones such as 250 have been prepared via Diels±Alder strategy using the BCB intermediate 248 and the quinone 249 (Scheme 139).…”