Lewis acid mediated (3 + 2) cycloadditions of donor-acceptor cyclopropanes with heterocumulenes.
نویسندگان
چکیده
Isocyanates, isothiocyanates, and carbodiimides are effective substrates in (3 + 2) cycloadditions with donor-acceptor cyclopropanes for the synthesis of five-membered heterocycles. These reactions exhibit a broad substrate scope, high yields, and well-defined chemoselectivity. Discussed herein are the implications of Lewis acid choice on the stereochemical outcome and the reaction mechanism.
منابع مشابه
Synthesis of cyclopentenones from cyclopropanes and silyl ynol ethers.
Five-membered carbocyclic rings appear in all classes of organic materials including pharmaceutical agents, polymers, natural products, and catalysts. Accordingly, their preparation has challenged synthetic chemists since the inception of the field. In this regard, [3+2] cycloadditions—both concerted and stepwise—represent convergent strategies for the formation of the cyclopentane nucleus. Dip...
متن کاملDivergent Reactivity of Thioalkynes in Lewis Acid Catalyzed Annulations with Donor-Acceptor Cyclopropanes.
Efficient methods for the convergent synthesis of (poly)cyclic scaffolds are urgently needed in synthetic and medicinal chemistry. Herein, we describe new annulation reactions of thioalkynes with phthalimide-substituted donor-acceptor cyclopropanes, which gave access to highly substituted cyclopentenes and polycyclic ring systems. With silyl-thioalkynes, the Lewis acid catalyzed [3+2] annulatio...
متن کاملLewis acid catalyzed [3 + 2] annulation of ketenimines with donor-acceptor cyclopropanes: an approach to 2-alkylidenepyrrolidine derivatives.
The [3 + 2] annulation reaction of C,C,N-trisubstituted ketenimines with donor-acceptor cyclopropanes bearing aryl, styryl and vinyl substituents at the C2 position, triggered by the Lewis acid Sc(OTf)3, supplies highly substituted pyrrolidines. Activated cyclopropanes fused to naphthalene and [1]benzopyrane nuclei are also suitable substrates in similar transformations, yielding partially satu...
متن کاملStereoselective Lewis acid mediated (3+2) cycloadditions of N-H- and N-sulfonylaziridines with heterocumulenes.
Alkyl and aryl isothiocyanates and carbodiimides are effective substrates in (3+2) cycloadditions with N-sulfonyl-2-substituted aziridines and 2-phenylaziridine for the synthesis of iminothiazolidines and iminoimidazolidines. Additionally, the stereoselective (3+2) cycloaddition of N-H- and N-sulfonylaziridines with isothiocyanates can be accomplished, allowing for the synthesis of highly enant...
متن کاملLewis acid-promoted cycloaddition reaction of cyclopropanes with allylsilanes.
The treatment of cyclopropanes having donor and acceptor substituents at the vicinal positions on the cyclopropane ring with a Lewis acid readily generates a 1,3-zwitterion, which reacted with allylsilanes to produce cycloadducts and allylic products. It was found that the yield of the cycloadduct depends on the steric demand of the alkyl substituents on the silicon atom.
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید
ثبت ناماگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید
ورودعنوان ژورنال:
- Organic letters
دوره 14 20 شماره
صفحات -
تاریخ انتشار 2012