Metal-Free, Regio- and Stereoselective Synthesis of Linear (E)-Allylic Compounds Using C, N, O, and S Nucleophiles

Abstract

A variety of allylic acetates and derivatives were synthesized by an efficient two-step protocol that employs readily available terminal alkenes as starting materials. This method is highly regio- and stereoselective, affording the linear (E)- isomer as the sole adduct. This process tolerates several functional groups including halogen-containing molecules, and it is general for weak oxygen, carbon, nitrogen, and sulfur nucleophiles. Furthermore, adducts were obtained in good to excellent yields.

One-Pot Synthesis of α-Alkyl Styrene Derivatives

“…Finally, 1-allyl-4-(trifluoromethyl)­benzene (strong EWG) gave the linear adduct B in 72% (entry 7) as the expected and sole product. Thus, corroborating our prior reports. , …”

“…On the basis of experimental observations, our previous work, , and the bromine-mediated rearrangements studies by Dubois and Costa, we propose that estragole undergoes an alkene bromination to form bromonium ion ( I ), which in turn undergoes an intramolecular attack by the electron-rich benzene to form the spiro[2.5] intermediate ( II ). This intermediate can be ring-opened by bromide ion to produce either 2,3-dibromo ( 2a , see the Supporting Information, SI) or 1,3-dibromide intermediate ( 2b ).…”

“…To optimize our protocol, we used estragole ( 1a ) as the model substrate, as shown in Table . Initially, 1a was subjected to our previously optimized bromination conditions . However, using CHCl 3 as a solvent produced a mixture of (di)­brominated products (∼ratio 1:1) .…”

“…The yields for the KO t Bu-mediated transformation are presented below in Tables –, whereas the yields using DBU are shown in the Supporting Information (Tables SI, 1–3). This study was performed to compare the result from our recently reported regio-and stereoselective nucleophilic addition to miscellaneous terminal olefins. , In our prior work, DBU was the best base to afford allylic adducts from electron-poor or weak electron-donating substrates. However, for this work, KO t Bu was deemed superior base for the observed rearrangement of electron-rich substrates (i.e., estragole and safrole).…”

Direct Allylation of Aliphatic Primary Amines via Al(OTf)3-Catalyzed One-Pot Four-Component Reaction

“…In 2015, Bugarin et al. developed an efficient two‐step protocol that employs readily available terminal alkenes as starting materials to synthesize allylamine derivatives in the presence of bromine …”