Regioselectivity of addition of thiols and amines to conjugated allenic ketones and esters

Abstract

Regioselectivity of nucleophilic addition to conjugated allenic ketones depends strongly on the nucleophile: anionic nucleophiles, e.g., triethylamine salts of benzenethiols, gave the /3-substituted /3,7-unsaturated ketones with high selectivity. In contrast, neutral nucleophile molecules, e.g., benzenethiols or aniline, afforded the ¡3-substituted ,/3-unsaturated ketones. The reactions to allenecarboxylic esters indicated the same regiochemical tendency, but lower selectivities were observed in the reactions with benzenethiol.

Addition of Primary Amines to 2‐(1‐Alkynyl)‐2‐cycloalken‐1‐ones

“…Unfortunately, we did not succeed in isolating or catching allene intermediate A by changing the reaction temperature, by using non‐nucleophilic bases, or by monitoring of the reaction by 1 H NMR spectroscopy. However, given that analogous selectivity in the addition of amines to conjugated allene ketones and esters was previously described, our proposed mechanism seems reasonable.…”

Carbonyliron Complexation and Carbonyl Insertion of Allenic Ketones

“…-Irradiation of CI -allenic ketones 5a [4], 5b [5], and 5d in the presence of an excess of [Fe(CO),] in hexane with a high-pressure Hg-lamp (Solidex filter) gave a mixture of red and yellow products which were chromatographically separated. The red crystalline products were shown to be the corresponding binuclear complexes 6a, 6b, (E)-and (Z)-6d, which are of type 1 (Scheme I)').…”

Revisiting the Addition of in‐situ Nucleophiles to Allenic Ketones: An Entry Towards Synthesis of Benzodioxins

“…At present, there are very few reports for the preparation of these above vinyl compounds. Sugita reported the formation of sulfides employing allenic ketone and thiol, but the main drawbacks were (1) formation of four different isomers depending upon starting materials and nucleophiles added, (2) reaction was carried out in deuterated solvents, (3) reaction was done in NMR tube, (4) limited substrate scope, (5) applicable to small scale synthesis (Scheme ).…”