Syntheses of the aphid pigment derivatives quinone A, quinone A′, and deoxyquinone A as racemates

Model Studies Towards Stephaoxocanes: Construction of the 2‐Oxa‐4‐aza‐ phenalene Core of Stephaoxocanidine and Eletefine

“…A similar transformation yielding a pseudoaxial chloride from the corresponding pseudoequatorial alcohol had previously been reported, employing a different set of reagents. [32] In our reaction, small amounts (Ͻ 5 %) of the dehydration product 18 were also isolated. This compound was recognized by the characteristic coupling between H-4 (δ ϭ 5.51 ppm, q, J ϭ 0.8 Hz) and Me-3 (δ ϭ 1.89 ppm, d, J ϭ 0.8 Hz).…”

“…This afforded 86 % of acetal 16, the spectroscopic data of which (J H-3,H-4 ϭ 2.4 Hz) provided evidence of configurational inversion. [32] Worthy of note is that the reaction proceeded without formation of the elimination product 18. It has been observed that this transformation is highly sensitive to steric bulk; [34] therefore, assuming that the reaction time required for completion is a measure of the steric hindrance at the benzylic center, this unusually slow reaction may imply that steric crowding was responsible for the reluctance of 12 and 15 to undergo reductive amination.…”

Role of the methoxy group in product formation via TiCl4 promoted 4-phenyldioxolane isomerizationsons

“…Our interest in naphthopyranquinones as potential antimicrobial and antibiotic agents has extended over two decades [1][2][3][4][5][6] as a result of their well documented importance. 7,8 Additionally, the synthesis of benzopyrans as model systems has received attention by ourselves 6,9-13 and others.…”

Synthesis of a protected 2-ethoxy-3-hydroxyethylfuran and its regioselectivity as a Diels–Alder diene on reaction with 3,5-dimethoxydehydrobenzene

“…[2][3][4] Such hydroxyethylnaphthalenes are frequently obtained by the acetylation, followed by reduction, of a precursor naphthalene in additional sequential steps that reduce overall yields. Furthermore, the correct regioselectivity for the acetylation has to be achieved.…”