Cross‐Metathesis Reactions of Homoallyl Methyl Malonates with Sterically Hindered Allylic Esters

Abstract

The methyl malonate esters of 3-buten-1-ol and 2-methyl-3-buten-1-ol can be coupled efficiently to different methallylic esters in the presence of the second-generation Grubbs catalyst to yield trisubstituted olefins by the cross-metathesis reaction. Product selectivity and yields depend on the relative

Diastereoselective Osmium‐catalyzed Vicinal Oxyamination of Acyclic Allylic Alcohol Derivatives

“…IR (thin film, cm rac-(2S,3R)-1-(Benzyloxycarbonylamino)-2-hydroxy-2,4-dimethylpentan-3-yl acetate (12c) and rac-(2R,3R)-1-(benzyloxycarbonylamino)-2-hydroxy-2,4-dimethylpentan-3-yl acetate (15c). The reaction was conducted according to general procedure 1 with rac-2,4-dimethylpent-1en-3-yl acetate (9c) 25 rac-(3S,4R)-Benzyl 2,4-dihydroxy-2-methylhexan-3-ylcarbamate (25b). The reaction was conducted according to general procedure 1 with rac-5-methylhex-4-en-3-ol (20b) 26 (50.0 mg, 0.44 mmol), potassium osmate dihydrate (6.50 mg, 0.02 mmol) and benzyl N-(4-tosyloxy)carbamate 1 (169 mg, 0.53 mmol).…”

“…Purification by flash chromatography (2% ethyl acetate/n-hexane) afforded the title compound 8b as a colorless oil ( rac-(2S,3R)-1-(Benzyloxycarbonylamino)-2-hydroxy-2-methylpentan-3-yl acetate (12b) and rac-(2R,3R)-1-(benzyloxycarbonylamino)-2-hydroxy-2-methylpentan-3-yl acetate (15b). The reaction was conducted according to general procedure 1 with rac-2-methylpent-1en-3-yl acetate (9b) 25 (56.0 mg, 0.39 mmol), potassium osmate dihydrate (5.80 mg, 0.02 mmol) and benzyl N-(4-tosyloxy)carbamate (1) (190 mg, 0.59 mmol). Purification by flash chromatography (30% ethyl acetate/ n-hexane) afforded rac-(2S,3R)-1-(benzyloxycarbonylamino)-2-hydroxy-2-methylpentan-3-yl acetate (12b) as a colorless oil (67.0 mg, 55%).…”

“…The reaction was conducted according to general procedure 1 with rac-2,4-dimethylpent-1en-3-yl acetate (9c)25 (60.0 mg, 0.38 mmol), potassium osmate dihydrate (5.70 mg, 15.5 μmol) and benzyl N-(4-tosyloxy)carbamate (1) (148 mg, 0.46 mmol). LRMS (ESI+) 424 ([424.2100, found 424.2099.rac-(2S,3R)-1-(Benzyloxycarbonylamino)-2-hydroxy-2,4-dimethylpentan-3-yl acetate (12c) and rac-(2R,3R)-1-(benzyloxycarbonylamino)-2-hydroxy-2,4-dimethylpentan-3-yl acetate (15c).…”

“…CDCl 3 ) 156.81, 136.60, 128.46, 128.10, 128.03, 107.25, 84.62, 81.05, 66.73, 45.23, 28.32, 26.50, 21.70, 21.08, 11.44. LRMS (ESI+) 330 ([M + Na] To a stirred suspension of rac-2,4-dimethylpent-1-en-3-ol (10c)25 (480 mg, 4.20 mmol) and sodium hydride (202 mg, 8.41 mmol) in dimethylformamide (3.0 ml) was added p-methoxybenzyl chloride (988 mg, 6.31 mmol) at room temperature under nitrogen. This reaction mixture was stirred until the reaction was complete.…”

Synthetic spirocyclic endoperoxides: new antimalarial scaffolds

“…Intermediate 22c was synthesized starting from 25, in turn prepared following a different synthetic approach by reacting Grignard reagent 23, formed in situ, with propargyl alcohol 24. 20 The resulting primary alcohol 25 was then converted to 22c via a mesyl ester intermediate that was sonicated in the presence of lithium iodide to afford the desired iodide 22c in good overall yield. Iodides 22a-c were used as alkylating agents for the enolate of lactone 19.…”