Stereochemistry and mechanism of acylation of acetylenes

Iron‐Catalyzed Synthesis of β‐Chlorovinyl and α,β‐Alkynyl Ketones from Terminal and Silylated Alkynes with Acid Chlorides

“…As well, the GaCl 3 -catalyzed reaction also proceeded with lower stereoselectivity. [2,5,13] Although the true mechanism is not yet known, we propose the following schemes to account for this FeCl 3 -catalyzed chloroacylation chemis- try, based on our observed results. In the catalytic reaction, FeCl 3 likely acts as a Lewis acid interacting with the carbonyl group in the acid chloride as shown in Scheme 1 and Scheme 2.…”

A Soft Vinyl Enolization Approach to α‐Acylvinyl Anions: Direct Aldol/Aldol Condensation Reactions of (E)‐β‐Chlorovinyl Ketones

“…[11] Although more studies are needed to expand the scope of the electrophiles, a salient feature of the current mild a-vinyl enolization of (E)-b-chlorovinyl ketones was well demonstrated upon the aldol reactions of diversely functionalized/substituted (E)-b-chlorovinyl ketones (3 g-3 l). [12] The access to such functionalized allenyl ketone derivatives is not currently possible by other "hard enolization" methods such as the direct lithiation of a-allenyl ketones [13] and strong base-promoted isomerization of alkynyl esters. [9] In particular, the employment of aliphatic (E)-bchlorovinyl ketones in our mild a-vinyl enolization approach highlights the unusual chemoselectivity in which a-vinyl enolization was preferentially performed over a-alkyl enolization (3 k-3 l).…”

Haloacylation of the Quintuple‐Bonded Group VI Metal Amidinate Dimers and Disproportionation of Acyl Groups to Form Carbynes

“…As illustrated in Scheme 1, exposure of acid halides RCOX (R = C 6 H 5 , 2-MeC 6 H 4 , Me; X = Cl, Br) to 1 in a 1:1 stoichiometric ratio at room temperature in diethyl ether for 10 min gives only one product (3)(4)(5)(6) for each acid halide, as shown by 1 H NMR spectroscopy. Four septet signals corresponding to the methine hydrogen atoms of eight isopropyl groups suggest two Mo atoms with different coordination environments.…”

“…[1,2] b-Chlorovinyl ketones are readily synthesized from alkynes and under acyl chlorides under the traditional Friedel-Crafts conditions. [1,3] Like the CÀC p bond, the metal-metal d bond is a twoelectron two-center bonds formed by the highest occupied molecular orbital, [4] thus the reactivity of quadruple-bonded dinuclear complexes has been highly anticipated. Although a large number of quadruple-bonded dinuclear species have been characterized in the past five decades, [5] their reactivity is far less explored.…”