A Sequential Route to Cyclopentenes from 1,6‐Enynes and Diazo Ketones through Gold and Rhodium Catalysis

Abstract

This work reports the construction of cyclopentene cores from 1,6‐enynes and aryl diazo ketones through two new reaction sequences involving initial gold‐catalyzed cyclization of 1,6‐enynes with diazo species, followed by rhodium‐catalyzed skeletal rearrangement of the resulting 3‐cyclopropyl‐2‐en‐1‐ones. In most instances the rhodium‐catalyzed reactions afforded cyclopentene derivatives whereas several n‐alkyl‐ or ortho‐substituted phenyl ketones delivered seven‐membered oxacycles. A plausible mechanism provides rationales for these two distinct products.magnified image

Gold-Catalyzed Synthesis of Small Rings

“…Later, Liu and co-workers reported that cyclopropyl gold carbenes generated in a 5- exo -dig fashion from 1,6-enynes can be trapped by aryl diazo ketones ( Scheme 35 B). 391 …”

Synthesis of Seven Membered Oxacycles: Recent Developments and New Approaches

“…This Obound enolate has a 16-electron configuration, being favorable for the final reductive elimination that leads to oxepines 125. [53] Scheme 29. A sequential route to oxepines 125 from 1,6-enynes 122 and diazo ketones 123 through gold and rhodium catalysis.…”

“…Adapted from ref. [53] In 2018, Hawkins and co-workers, exploited a method previously developed by them, [54] in combination with a cyclization under Mitsunobu conditions, [55] to get access to the oxepinefused flavone 133. [56] As depicted in Scheme 30, the first reaction transforms the cyclopropane 132 into the alcohol 137.…”

“…This O‐bound enolate has a 16‐electron configuration, being favorable for the final reductive elimination that leads to oxepines 125 . [ 53 ]…”

A convenient and practical synthesis of β-diketones bearing linear perfluorinated alkyl groups and a 2-thienyl moiety

“…А number of different combination of solvents, bases and reaction conditions were described in literature for this condensation. For example, t -BuOK in benzene [16], NaOMe in methanol [17], NaH in Et 2 O [18], NaH in THF [19], NaOMe in Et 2 O [20] or LiHMDS in THF [21] were tested. The yields varied from 32 to 87%.…”