Radical [3 + 2]-Annulation of Divinylcyclopropanes: Rapid Synthesis of Complex Meloscine Analogs

Abstract

A radical [3+2]-divinylcyclopropane annulation cascade has been extended to encompass five D-ring variants of the meloscine/epimeloscine core structure. Representative ABCD tetracyclic intermediates were further elaborated with novel substituted E-rings through subsequent transformations of advanced intermediates that provided opportunities for late-stage variation of the B- ring (lactam) N-substituents which were also developed.

Copper‐Catalyzed β‐Iodovinylation of Carbamates: Expedient Access to Highly Functionalized Vinyl‐Carbamates

“…β‐Iodovinyl‐carbamates are key intermediates that are used to access a vast array of β‐functionalized vinyl‐carbamates via functionalization of their vinyl iodide moiety ,. One strategy for the synthesis of β‐iodovinyl‐carbamates consists in iodinating the corresponding enecarbamates using an iodonium source such as iodine, iodine monochloride or N ‐iodosuccinimide (Scheme a) ,–. In a complementary approach, Wada and co‐workers reported the synthesis of β‐iodovinyl‐carbamates through iodocyclization of a carbamate onto an alkyne using IPy 2 PF 6 as the iodonium source (Scheme a) .…”

“…As mentioned previously, β‐iodovinyl‐carbamates are key intermediates in many organic transformations. For example, β‐iodovinyl‐carbamates have been used in various metal‐catalyzed C–C bond forming reactions such as Suzuki,–, Sonogashira,, Heck, Stille, and Nozaki–Hiyama–Kishi . To the best of our knowledge, they are no reports of their use in C‐heteroatom bond forming reactions.…”

The chemistry of the carbon-transition metal double and triple bond: Annual survey covering the year 2014

“…246) [638]; (3) five-and six-membered ring lactams that contain fluorinated alkene groups [639]; (4) five-and six-membered ring unsaturated lactams for total syntheses of indolizidinone and quinolizidinone derivatives [640]; (5) five-and six-membered ring amines for preparation of cyclic α-amino acid derivatives [641]; (6) tetrahydropyridines [642,643], including those employed in total syntheses of meloscine analogs (e.g. 247) [644], cryptopleurine [645], leuconoxine, leuconodine B, melodinine E (in a diastereoselective RCM) (e.g. 248) [646], key six-membered ring components of ibogamine and tronocarpine [647], alkaloid 205B (includes a cross metathesis with cis 1,4-diacetoxy-2-butene in an earlier step) [648], 3-epi-fagomine and related compounds [649], conhydrine [650], and 7-epi-castanospermine [651];…”

NHC-Boryl Radical Catalysis for Cycloisomerization With C–C Triple Bond Reorganization

“…This catalysis has shown significant applications in the synthesis of five-membered ring molecules [15][16][17][18][19] and related natural products. [20][21] Recently, Maruoka 22 disclosed an elegant enantioselective synthesis using a chiral thiol as the precatalyst. Despite these advances, the exploitation of other new radical catalysts and reaction modes for remarkable molecular transformations has rarely been achieved.…”