Catalyst-Free α-Allylation of Dihydroisoquinolines with Morita–Baylis–Hillman Carbonates and Its Applications in the Construction of Benzo[a]quinolizidines

Abstract

In this work, a mild and efficient catalyst-free α-allylation of 3,4-dihydroisoquinoline imines with Morita−Baylis− Hillman (MBH) carbonates was reported. The scopes of 3,4-dihydroisoquinolines and MBH carbonates as well as gram-scale synthesis were investigated, and densely functionalized adducts were obtained in moderate to good yields. The synthetic utility of these versatile synthons was further demonstrated by the facile synthesis of diverse benzo[a]quinolizidine skeletons.

Modular Approach to Highly Substituted 3-Methylpyridones

“…Initially, Baylis−Hillman amine 3a and methyl 2-oxopropanoate 4a were selected as model substrates to optimize the condensation reaction, and the results are summarized in Table 1 (see the Supporting Information for an extensive sampling). We first tested the refluxing toluene with a Dean− Stark trap condition employed in the aldehyde system (entry 1), 21 but unfortunately, only 23% yield of desired 3methylpyridone 5a was obtained from the resulting complex mixture. Changing the solvent to xylene increased the yield to 27% (entry 2).…”

“…In 2015, our group disclosed an intramolecular iminium ion cyclization reaction of Baylis–Hillman amines and aldehydes to generate diverse 3-carboxy-4,5-dihydropyrroles . As part of our continuing interest in the utilization of Baylis–Hillman derivatives, we herein report a modular approach to synthesize highly substituted 3-methylpyridones from Baylis–Hillman amines and ketones in one pot under benzoic acid catalysis (Scheme B).…”

Synthesis of Quinolinoneylnitrones and Coumarinylnitrones via a Cascade Hydroamination and Aza-MBH-Type Reaction

“…Then, the Lin group described a new method for the construction of functionalized furo­[3,2- c ]­coumarins via domino MBH-type/Wittig reaction . Thereafter, some interesting cascade procedures for the MBH- or aza-MBH-type reaction were gradually reported. − However, there have been very few studies of the preparation of nitrones through a cascade method.…”