A Convenient Synthesis of 7-Acetoxyheptanal and 6-Methylheptanal

Drug Development of the Antimalarial Agent Artemisinin: Total Synthesis, Analog Synthesis, and Structure-Activity Relationship Studies

“…18 As outlined by Roush and Walts, 19 the sulfoxide 21 was converted to the corresponding dianion with lithium diisopropylamide (LDA) and alkylated with n-butyl iodide to provide a diastereomerically complex mixture that was then converted directly to 2-butyl-3R-methylcyclohex-2-en-l-one (50% yield, 60: la mixture at C-2) upon thermolysis. We found that sulfoxide 21 could be alkylated with 2-(2-bromoethyl)-2,5,5-trimethyl-l,3-dioxane 20 and that the resultant complex mixture could be desulfurized with aluminum amalgam to furnish the desired ketone H in 40-50% yield as a 9:1 ((3:a) mixture at C-2. Surprisingly, alkylation of this sulfoxide dianion was not improved using 2-(2-iodoethyl)-2,5,5-trimethyl-l,3-dioxane in place of the bromide.…”

Chromium-Templated Synthesis of Densely Substituted Distorted Arenes − Intramolecular Benzannulation of [(Alkynylaryl)alkenyl]carbene Complexes to Planar-Chiral Hydroquinoid [2.2]Heterametacyclophanes

“…1 [23] After evaporation of the solvent and chromatographic workup on silica gel with cyclohexane/tert-butyl methyl ether (1:1; R f ϭ 0.8), N-but-2-ynyl-3-iodo-N-methylaniline (11; 12.7 g, 44.5 mmol, 90%) was obtained. 1 [42] tBuLi (20 mmol) was added slowly at Ϫ78°C to a solution of alkyne 9Ϫ12 (10 mmol) in tetrahydrofuran (30 mL). The mixture was stirred for 2 h, during which a colour change from yellow to red took place, and it was transferred by syringe into a solution of 2-(2-bromoethyl)-1,3-dioxane (1.6 mL, 12 mmol) in tetrahydrofuran (50 mL) and allowed to warm up to Ϫ30°C.…”

2-(2-Bromoethyl)-1,3-dioxane

“…As noted above (eq 18), (1-MgBr) and (2-MgBr) give coupling reactions with halides and tosylates under conditions of copper catalysis. 38, 50 Cuprate formation also results in successful condensation with allylic acetates (eq 23), 51,52 epoxides, 53 vinyl epoxides (eq 24), 54 and alkynes (eq 25). 55 Conjugate addition to α,β-unsaturated ketones can also be realized in this way, 56 this process often constituting the first step of an annulation sequence.…”