Gold-Catalyzed Highly Diastereoselective Synthesis of Functionalized 3,4-Disubstituted ButyrolactamsviaPhosphatyloxy or Carbonate Double Migrations

Gold-Catalyzed C(sp2 )-C(sp) Coupling by Alkynylation through Oxidative Addition of Bromoalkynes

A gold(I)-catalyzed cascade cyclization-alkynylation of allenoates using alkynyl bromide to generate β-alkynyl-γ-butenolides was investigated. Whereas alkynyl iodides afforded significant amounts of the homo-coupling of two lactone units, alkynyl bromides led to a selective reaction, and a broad functional group tolerance was observed. Under the optimized reaction conditions, it was possible to directly synthesize a large range of β-alkynyl-γ-butenolides in moderate to good yields without the need for any external oxidant.

Activation of alkynes with B(C₆F₅)₃--boron allylation reagents derived from propargyl esters

Novel allyl boron compounds are readily synthesized via rearrangement reactions between Lewis acidic B(C6F5)3 and propargyl esters. These reactions proceed through an initial cyclization followed by ring-opening and concurrent C6F5-group migration. In the absence of disubstitution adjacent to the ester oxygen atom, an allyl boron migration rearrangement leads to formal 1,3-carboboration products. These allyl boron compounds act as allylation reagents with aldehydes introducing both a C3-allyl fragment and a C6F5-unit as a single anti-diastereomer. In these reactions, B(C6F5)3 activates the alkynes, prompting the rearrangement processes and enabling installations of C6F5 and R-groups.

Gold-catalysed cyclisation of N-propargylic β-enaminones to form 3-methylene-1-pyrroline derivatives

A gold(i) catalysed reaction between N-propargylic β-enaminones and arynes was developed to access 3-methylene-1-pyrrolines. The title compounds were obtained in 57–78% yields.

Recent progress towards transition metal-catalyzed synthesis of γ-lactams

The scope of transition metal-catalyzed synthesis of functionalized γ-lactams has broadened tremendously in the last decade (see the picture). These metal-catalyzed processes are reviewed by highlighting their specificity and applicability, and the mechanistic rationale is presented where possible.

Dehydrogenative Meyer-Schuster-like rearrangement: a gold-catalyzed reaction generating an alkyne

Easily accessible propargylic esters are converted to the inverted alkynyl ketones in an oxidative gold-catalyzed reaction. Gagosz's catalyst in combination with PhI(OAc)2 is the best system for this conversion and 18 examples with yields up to 80 % are reported. The results indicate that the triple bond in the product is formed by elimination from a vinylgold intermediate. In a formal sense the new conversion overall is a dehydrogenative Meyer-Schuster rearrangement.