Direct and stereospecific synthesis of allenes via reduction of propargylic alcohols with Cp2Zr(H)Cl.
نویسندگان
چکیده
Allenes can be synthesized via the direct SN2' addition of hydride to propargylic alcohols. Previous examples of this approach, however, have involved harsh reaction conditions and have suffered from incomplete transfer of central chirality to axial chirality. Here we show that Cp2Zr(H)Cl can react with the zinc or magnesium alkoxides of propargylic alcohols to generate allenes in good yield and in high optical purity. Dialkyl-, alkyl-aryl-, and diaryl-allenes are accessible by this method. Furthermore, the reaction can provide silyl-substituted allenes, trisubstituted allenes, and terminal allenes.
منابع مشابه
The synthesis of allenes by Cu(I)-catalyzed regio- and stereoselective reduction of propargylic carbonates with hydrosilanes.
Cu(I)-catalyzed anti-S(N)2'-type reduction of internal propargylic carbonates with hydrosilanes affords various di- and trisubstituted allenes with high regioselectivities; the reactions are compatible with functional groups and work efficiently for the synthesis of optically-active allenes.
متن کاملSynthesis of mono- and 1,3-disubstituted allenes from propargylic amines via palladium-catalysed hydride-transfer reaction.
Mono- and 1,3-disubstituted allenes were synthesized from the corresponding propargylamines via palladium-catalysed hydride-transfer reaction. In the current transformation, propargylic amines can be handled as allenyl anion equivalents and introduced into various electrophiles to be transformed into allenes under palladium-catalyzed conditions.
متن کاملNaHSO4-SiO2: An Efficient Reusable Green Catalyst for Selective C-3 Propargylation of Indoles with Tertiary Propargylic Alcohols
Although several methods for the preparation of 4o propargyl indole derivatives have been published, this synthetic transformation is complicated by the tendency of 3o propargyl alcohols to form allenium intermediates in acidic media. It is therefore a challenge to find an efficient method for the C-3 propargylation of indoles with 3° propargylic alcohols. In this pa...
متن کاملBatch and Flow Synthesis of Pyrrolo[1,2-a]-quinolines via an Allene-Based Reaction Cascade.
An efficient reaction cascade delivering a series of pyrrolo[1,2-a]quinolines bearing phosphonate or phosphine oxide moieties is presented. This sequence exploits the in situ transformation of propargylic alcohols into transient allenes by means of a strategic [2,3]-sigmatropic rearrangement followed by trapping of the resulting allenes by an adjacent pyrrole ring. Furthermore, the initial smal...
متن کاملDirected hydrozirconation of propargylic alcohols.
Hydrozirconation of alkynes with Cp2ZrH(Cl) (Schwartz reagent) generates vinyl zirconium species reliably, stereospecifically, and regioselectively. These organometallic reagents can participate in cross-coupling reactions, conjugate and nucleophilic additions, and can undergo carbonylation and halogenation.1 Hydrozirconation of terminal alkynes often proceeds with >50:1 selectivity to form the...
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:
- Journal of the American Chemical Society
دوره 130 33 شماره
صفحات -
تاریخ انتشار 2008