Rearrangement and Substitution of Pentadienyl Groups in Homopentadienylamines on Treatment with Organolithium Reagents

Abstract

(4R,5R)‐N,N′‐Bis[(1S)‐1‐phenylethyl]‐3,6‐divinyl‐1,7‐octadiene‐4,5‐diamine underwent rearrangement and/or substitution of one/two pentadienyl groups on treatment with 2−4 equiv. of an organolithium reagent (nBuLi, PhLi) in THF. By careful choice of experimental conditions, C1‐ or C2‐symmetric 1,2‐disubstituted 1,2‐diamines could generally be obtained with good stereocontrol. It is proposed that the reaction proceeds through competitive pathways involving a 1,3‐shift of the branched homopentadienyllithium amide moiety with retention of configuration and retro‐pentadienyllithiation to form an intermediate imine. In contrast, only rearrangement was observed on treatment of (1R,S)‐N‐[(1S)‐1‐phenylethyl]‐1‐(2‐pyridyl)‐2‐vinyl‐3‐butenylamine with 2 equiv. of nBuLi at −78 °C.

3-Bromopropenyl Esters in Organic Synthesis: Indium- and Zinc-Mediated Entries to Alk-1-ene-3,4-diols

“…The Indium Route to Alk-1-ene-3,4-diols: Simple Diastereoselectivity. Since it is known that the allylmetalation of aldehydes, as well as of imines, is a reversible process, we checked the de values after different time intervals in two reactions, using benzaldehyde and cyclohexancarboxaldehyde, respectively, to ascertain whether the different diastereoselectivities observed with conjugated and unconjugated aldehydes are the result of thermodynamic equilibration. Quenching experiments at different reaction times (5, 10, 30, 60, 120, and 1200 min) following the experimental procedure reported in Table (entries 1 and 6) unambiguously show that there was no change in diastereomeric excess in both cases.…”

Octa‐1,7‐diene‐4,5‐diamine Derivatives: Useful Intermediates for the Stereoselective Synthesis of Nitrogen Heterocycles and Ligands for Asymmetric Catalysis

“…On the other hand, 1,8‐disubstituted derivatives 70 were directly converted into 3,6‐disubstituted 2,5‐diazabicyclo[2.2.1]heptanes 71 by using only one equivalent of iodine, and addition of another equivalent of iodine did not change the composition of the reaction mixture (Scheme ). Moreover, since the branched 3,6‐disubstituted octa‐1,7‐diene‐4,5‐diamines 72 served to prepare unsymmetrically 1,2‐disubstituted 1,2‐diamines 73a – d , these compounds were submitted to iodine‐promoted cyclization and the expected bridged piperazines 74a – d were obtained in satisfactory yields. Removal of one nitrogen substituent was obtained by using ammonium formate in refluxing ethanol; e.g., the preparation of compounds 75a , b from 71a and 74a (Scheme ).…”