Diastereoselective Intramolecular Hydride Transfer Triggered by Electrophilic Halogenation of Aryl Alkenes

Abstract

Diastereoselective hydride transfer could be triggered by electrophilic halogenation (bromination or fluorination) of homoallylic alcohol O-Bn ethers. The resulting diastereomerically enriched haloalkyl alcohols underwent subsequent intramolecular nucleophilic substitution to afford the corresponding tetrahydrofurans. ASSOCIATED CONTENT Supporting InformationThe Supporting Information is available free of charge on the ACS Publications website.Crystallographic data for compound 2j (CIF) Crystallographic data for compound 3n-Br (CIF) Experimental procedures, spectral data (PDF)

Alkyl amines and ethers as traceless hydride donors in [1,5]-hydride transfer cascade reactions

“…The synthesized products include functionalized allenes, cycles, and alcohols. Based on three types of hydride acceptors, namely [Au]-activated alkynes, 46–48 [Re]-vinylidene, 49–51 and carbocations, 52–54 these developed reports can be classified into three categories, as outlined in Scheme 23.…”

“…In 2019, a novel diastereoselective [1,5]-HT cascade reaction triggered by electrophilic bromination or fluorination, was established by Chiba and co-workers (Scheme 33). 54 In the presence of an electrophilic halogen source (NBS or Selectfluor), the homoallylic alcohol O-Bn ethers 82 evolved into halonium ions 84 which were in equilibrium with carbocations 85 . Then carbocation-initiated stereoselective [1,5]-HT occurred via a six-membered chair-like transition state 86 and gave oxocarbenium ions 87 .…”

Highly efficient synthesis and NMR features of novel fused pyrimidothiazinium trihalogenides

“…Moreover, this methodology allows receiving polycyclic heterocycles containing a residue of electrophile which can be reasoned biological activity of target heterocycles [11–14]. On the other hand, the halogens are convenient electrophilic reagents, which are widely used in heterocyclic chemistry [15–19]. In our previous work, we have established that electrophilic halogencyclization of terminally unsubstituted alkenyl (thio‐)ethers of fused heteroarylpyrimidinones results in the annulation of the thiazoline ring [20–26].…”

Leveraging Electron‐Deficient Iminium Intermediates in a General Synthesis of Valuable Amines

“…Here, we present the leveraging of highly electrondeficient iminium ions in the synthesis of valuable trifluoromethylated amines, aminoesters and aminophosphonates by hydroaminoalkylation of unactivated alkenes and alkynes. Our concept relies on the pairing of a rapid intermolecular aza-Prins-like reaction of these electrondeficient species with a stereoselective internal reduction event (1,5-hydride transfer) [18,[20][21][22][23] ensuring that CÀ C bond formation is coupled to reduction in a redox-neutral manner and, contrasting the methods described before, without requiring an external reductant (Scheme 1d). This strategy enables the preparation of a broad range of valuable amines and late-stage functionalization of complex architectures.…”