Nonracemic Bicyclic Lactam Lactones via Regio- and cis-Diastereocontrolled C−H Insertion. Asymmetric Synthesis of (8S,8aS)-Octahydroindolizidin-8-ol and (1S,8aS)-Octahydroindolizidin-1-ol
摘要:
The Rh-2(MPPIM)(4)-catalyzed intraniolecular C-H insertion reaction of (S)- and (R)-1-benzyl-5-(alpha-diazoacetoxy)piperidin-2-one and (S)-1-benzyl-4-(alpha-diazoacetoxy)pyrrolidin-2-one proceeds with high regioselectivity and cis-diastereoselectivity to give good yields of chiral nonracemic bicyclic lactam lactones (BLLs). For (S)- and (R)-1-benzyl-5-(alpha-diazoacetoxy)piperidin-2-one, the regio selectivity of the C-H insertion is catalyst-dependent; for example, (S)-1-benzyl-5-(alpha-diazoacetoxy)piperidin-2-one undergoes C-H insertion at C-6 preferentially when Rh-2(5S-MPPIM)(4) is used, but with Rh-2(5R-MPPIM)(4), C-H insertion occurs preferentially at C-4. This effect is not observed in the reaction of (S)-1-benzyl-4-(alpha-diazoacetoxy)pyrrolidin-2-one. The utility of the BLLs as chiral building blocks in alkaloid synthesis is exemplified by the synthesis of (8S,8aS)-octahydroindolizidin-8-ol and (1S,8aS)-octahydroindolizidin-1-ol.
<i>N</i>-Trialkylsilyl Bistrifluoromethanesulfonimides (R<sub>3</sub>SiNTf<sub>2</sub>) Are Powerful Catalysts for the Highly Efficient α-Amido Alkylation Reactions of Silicon-Based Nucleophiles
作者:Raja Ben Othman、Till Bousquet、Mohamed Othman、Vincent Dalla
DOI:10.1021/ol052357j
日期:2005.11.1
In situ formed N-trialkylsilyl bistrifluoromethanesulforlimides (R3SiNTf2) species have been shown to efficiently catalyze the nucleophilic substitution reactions of chiral 5-oxypyrrolidin-2-ones by silicon-based nucleophiles. The reaction rates were significantly accelerated in comparison to the cases where the usual triflate catalysts are used. Adducts were obtained in high yields and usual stereoselectivities within short reaction times, and the process was compatible with a semipreparative scale.
Toward Improving the Chemistry of <i>N</i>-Acyliminium Ions: Nucleophilic Substitution Reactions of Pyrrolidinone Derivatives with Trialkylsilyl Nucleophiles Catalyzed by Triisopropylsilyltrifluoromethane Sulfonate (TIPSOTf)
作者:Raja Ben Othman、Till Bousquet、Anthony Fousse、Mohamed Othman、Vincent Dalla
DOI:10.1021/ol050576z
日期:2005.7.1
Nucleophilic substitution reactions of racemic and chiral 5-acetoxy-, 5-ethoxy-, and 5-methoxypyrrolidin-2-ones by silicon-based nucleophiles were efficiently catalyzed by TIPSOTf. This process was found to be general and accommodates a broad range of substrate-nucleophile combinations.