A procedure for gas-phase dehalogenation of organic dihalides with alkali metal vapors using microwave and/or ultrasound excitation and matrix isolation of products

Abstract

Gas-phase dehalogenation of organic dihalides with alkali metal vapors in excess argon is promoted by microwave and/or ultrasound excitation. The products were deposited on a cold window along with excess solid argon. The use of the method is demonstrated on three , -diiodoalkanes. The procedure is useful for the preparation of small amounts of highly strained olefins and ring compounds from their dihalo precursors.Biradicals and biradical-like species are believed to play many photochemical processes encountered in organic a pivotal role in various thermal processes and in very chemistry.2-4 In spite of their generally acknowledged

Combined Microwaves/Ultrasound, a Hybrid Technology

“…30 years ago, Otteson and Michl described a pioneering gas-phase dehalogenation of organic dihalides using alkali metal vapours in excess argon under MW/US irradiation [12]. Several examples of this marriage appeared in the literature in the decades that were to come as innovative approaches to classical organic reactions and metal-assisted catalysis were described [13].…”

The Combined Use of Microwaves and Ultrasound: Methods and Practice

“…Probably the first indication of the power of MW and US excitation in organic synthesis was reported as early as 1984 by Otteson and Michl [32]. The gas-phase dehalogenation of organic dihalides with alkali metal vapor in excess argon was carried out under MW or US irradiation with two different dehalogenation apparatus setups fabricated from borosilicate glass.…”

Matrix Isolation

“…31,32 The technique has been described in some detail by Otteson and Michl. 33 Matrix-isolated alkali atoms (or small clusters) also undergo easy photoionization, and the electrons released in this process may attach themselves to nearby substrates to form the corresponding radical anions. 34 However, one drawback of alkali metal atoms or clusters is that they tend to swamp the electronic absorption spectrum of the target reactive intermediate that can only thus be detected by IR.…”

“…Dehalogenations can also be carried out by cocondensation of dihalides (usually diiodides) with alkali atoms. 33 This strategy has been followed to generate such species as the highly twisted adamantene 93 or the strongly pyramidalized tricyclo[3.3.1.0 3,7 ]nonene 94 shown in Scheme 17.9. Dehydrohalogenations (elimination of HX) can in turn be effected by passing the halide over a solid base such as vacuum-dried hot KOH 95 or t-BuOK 96 adsorbed on some carrier material.…”