The Behaviors of Metal Acetylides with Dinitrogen Tetroxide

Abstract

Lithium phenylacetylide (1a) and N 2 O 4 (2) at À 788 yield diphenylbutadiyne (6a) by oxidative coupling, phenylacetylene (7a) by oxidation and then solvent H-abstraction, and benzoyl cyanide (8) by dimerizativerearrangement of nitroso(phenyl)acetylene (23). Nitro(phenyl)acetylene (3, R Ph) is not obtained. Benzonitrile (9), a further product, possibly results from hydrolytic decomposition of nitroso(phenyl)ketene (27) generated from phenylacetylenyl nitrite (26). Phenylacetylene (7a) and 2 give, along with (E)-and (Z)-1,2-dinitrostyrenes (34 and 35, resp.), 3-benzoyl-5-phenylisoxazole (10), presumably as formed by cycloaddition of benzoyl nitrile oxide (40) to 7a. Further, 2 reacts with other lithium acetylides (1b ± 1e), and with sodium, magnesium, zinc, copper, and copper lithium phenylacetylides, 1f ± 1l, to yield diacetylenes 6a ± 6c and monoacetylenes 7a ± 7c. Conversions of metallo acetylide aggregates to diacetylenes are proposed to involve generation and addition reactions of metallo acetylide radical cationic intermediates in cage, further oxidation, and total loss of metal ion. Loss of metal ions from metallo acetylide radical cations and H-abstraction by noncaged acetylenyl radicals will give terminal acetylenes. The principal reactions (75 ± 100%) of heavy metal acetylides phenyl(trimethylstannyl)acetylene (44) and bis(phenylacetylenyl)mercury (47) with 2 are directed nitrosative additions (NO ) and loss of metal ions to give nitroso(phenyl)ketene (27), which converts to benzoyl cyanide (8).Introduction. ± The present study primarily involves the behaviors of metal acetylides (1) , respectively, are unsatisfactory; acetylenyl nitrites 4 are unknown. Investigation has also been made of 1) other products formed from 1 and 2, and 2) the reactions of 2 with phenylacetylene (7, R Ph):

Oxidative Homocoupling of Aryl, Alkenyl, and Alkynyl Grignard Reagents with TEMPO and Dioxygen

“…Moreover, we found that the oxidative homocoupling of vinyl Grignard reagents to provide dienes is possible with TEMPO: b-Styrylmagnesium chloride and C 6 H 13 CH=CHMgCl were transformed into the dienes 1 k and 1 l, respectively ( Table 1, entries 15 and 16). Alkynyl magnesium compounds also underwent TEMPO-mediated coupling; [6] however, longer reaction times (4-6 h) were necessary. At room temperature, the homocoupling of C 6 H 5 CCMgBr was very slow ( Importantly, we found that TEMPO-MgBr (2), which was formed as a by-product, was reoxidized readily to TEMPO with dioxygen in refluxing THF within 10 min, as indicated by TLC [Eq.…”

Oxidative Homokupplung von Aryl‐, Alkenyl‐ und Alkinyl‐Grignard‐Reagentien mit TEMPO und Sauerstoff

“…15,16). Auch Alkinylmagnesiumverbindungen ließen sich mit TEMPO unter Homokupplung umsetzen 6. Allerdings waren hierzu längere Reaktionszeiten erforderlich (4–6 h).…”

Nitroalkynes: A Unique Class of Energetic Materials

“…8,9 In 1996, Woltermann et al treated a host of phenylacetylides with various nitrating agents in a futile attempt at creating 7 (Scheme 7). 16,54 One should note that Schmitt had already remarked in 1987 that 'addition of nitronium One of the serendipitous outcomes of these experiments when employing dinitrogen tetroxide with (phenylethynyl)lithium (38), (phenylethynyl)zinc bromide (39), and (phenylethynyl)magnesium bromide (40) was an interesting oxidative coupling to diphenylbutadiyne (41). This process involves a likely initial one-electron oxidation to the phenylethynyl radical, a notion supported by the observation of hydrogen abstraction from the solvent to give varying amounts of phenylacetylene (42).…”

“…Some examples are shown in Scheme 8. 16,54 Scheme 8 One-electron oxidation of metal phenylacetylides by dinitrogen tetroxide Despite the litany of failures summarized in this section, the nitration of alkynes, in particular certain stannyl and silyl derivatives, constitutes one of the most effective entries into the class of nitroalkynes (see section 4.2.1).…”

“…Motte, in his thesis 53 and in a publication with Viehe in 1975, 15 also accomplished what Robson, Tedder, and Woodcock had been unable to do in 1968, 13,51 namely to oxidize a nitroso-to a nitroalkyne. Thus, 24 was transformed into 3 when treated with either hydrogen peroxide or peracetic acid, in up to 40% yield (Scheme 21 Scheme 22 suggests that, under certain conditions, dinitrogen tetroxide might act as NO + NO 3 in an electrophilic manner, 16,54 rather than as a source of NO 2…”