Science of Synthesis

Heaney, H.; Christie, S., Science of Synthesis, (2004) 3, 378.

The preparation and reactions of alkynylcopper(I) derivatives are reviewed in a number of monographs that are devoted to the chemistry of alkynes.[‌472‌–‌474‌] The first report of a copper(I) derivative of an acetylene involved the formation of the very explosive red precipitate which was obtained when illuminating gas was passed through a solution of copper(I) chloride in aqueous ammonia.[‌26‌] Acetylene was subsequently obtained by hydrolysis of what turned out to be copper acetylide (Cu2C2).[‌475‌] Copper acetylide is not very useful as a synthetic intermediate and the monocopper(I) derivative of acetylene cannot be prepared directly. This latter difficulty can be circumvented by generating a copper(I) derivative of an alkyne that carries an easily removable group such as a formyl group or its equivalent.[‌476‌] Although all alkynylcopper(I) reagents, for example propynylcopper(I), are very explosive, some, such as phenylethynylcopper(I), are relatively stable species when kept in the absence of air. It is well-known that the oxidative dimerization of alkynylcopper(I) reagents proceeds in the presence of a range of oxidizing agents. Indeed, the oxidation of (phenylethynyl)copper(I) to 1,4-diphenylbuta-1,3-diene is a venerable reaction, originally using air.[‌477‌,‌478‌] An early example of Glaser coupling involved the synthesis of indigo in which the key step was the coupling of (2-nitrophenyl)acetylene using potassium ferricyanide as the oxidant.[‌479‌,‌480‌] Other oxidizing agents have also been used and will be mentioned at appropriate points: they include copper(II) salts,[‌481‌] potassium manganate(VII),[‌482‌] and peroxides.[‌483‌,‌484‌] The prediction[‌485‌] that polyalkynes could be prepared by Glaser coupling has evidently been justified,[‌486‌] and will be exemplified in more detail in later sections. A review of early work discusses and tabulates reactions that involve the oxidation of preformed copper(I) derivatives of alkynes, as well as examples where the intermediates were not isolated.[‌487‌] Glaser coupling reactions and other routes to conjugated di- and polyynes are also discussed in a review.[‌488‌] The preparation of alkynylcopper(I) reagents in aqueous ammonia frequently proceeds easily and in good yield and hence gives useful synthetic intermediates. A large number of substitution reactions that involve copper(I) acetylides are tabulated in reviews.[‌131‌,‌489‌] A report of the preparation of (phenylethynyl)copper(I) in 98% yield involved the treatment of ammonium tetrakis(phenylethynyl)borate with a solution of copper(I) chloride in aqueous ammonia.[‌490‌,‌491‌] However, it may be made more conveniently directly from phenylacetylene in almost as good a yield.[‌492‌] The preparation of (phenylethynyl)copper(I) is available as a checked procedure: the compound is reported to be stable over a long period of time when stored under nitrogen in a brown bottle.[‌493‌] Although the majority of the reactions studied have involved reactions with aryl halides, there are examples where alkenyl halides and alkynyl halides undergo coupling reactions. For example, (phenylethynyl)copper(I) gives acceptable to very good yields in coupling reactions with a number of iodoalkenes[‌494‌,‌495‌] and with halogenoalkynes.[‌496‌] Substitution reactions that involve sulfenyl or acyl halides also proceed under relatively mild conditions. For example (2,4-dinitrophenyl)sulfenyl chloride gives 2,4-dinitro-1-[(phenylethynyl)sulfanyl]benzene in 80% yield and 3-phenylpropanoyl chloride gives with pentynylcopper(I) the 1-phenyloct-4-yn-3-one in 81% yield.[‌497‌] However, halogen derivatives such as N-bromosuccinimide that undergo homolysis easily do not give substitution products, but give rise to oxidative coupling products. Thus, (phenylethynyl)copper(I) with N-bromosuccinimide gives 1,4-diphenylbuta-1,3-diyne.

Meeeeeeeeeee eeeeeeeee ee ee ee8 eeeeee eeeee eeeeeeeeee eeeeeeee eeee eee eeeeeeeee eeee eeee Meeeeeee (Meeeeee ‌8.8.8.8.8‌) ee eeeeeeeeeee eeeeeeee (Meeeeee ‌8.8.8.8.8.8‌) eee eeee-eeeeeeeeeee ee eeee eee eeeeeeeee eeee eeeeeee, eee eeeeeee, “Meeeee eeeeeeee”. Me eee eeeee eeee, eeeeeeeeeeeee(M) eeeeeeee ee eee eeeee ee ee ee8 eeeeee eeeee eeeeeeeeee eeee ee eeeee eeeee eeeeeeee eeee eeee eeeeeee. Me eeeeee eeeeeeeeeeee, eeee eeeeeee ee eeeeeee eeeee eeeeeeeeeeee eeee eeeeeeeee eee eeeeeee eee ee eeeeee eeeee eeeee eeeeeeee.[‌888‌] Meeeeeeee ee (eeeeeeeeeeeee)eeeeee(M) eeee eeeee eeeeeee eee eeeeee eeeeeee eeee eeee eeeeee ee eeeeeeeeeeee eeeeeeee, ee eeeee ee ‌Meeeee 88‌. Meeeeeeee ee α-eeee eeeeeee eeee eeeeeeeeeeeee(M) eeeeeeee eee eeee ee eeeeeeee; eeee eeeeee ee eee eeeeee eeeeeeeee ee eeeee eeeeeeeeeee ee e eeeeee ee eee eeee ee eeeeee-eeeeeeeee eeeeeeeeeee ee eee eeeeeeee eeeee. Meeeeeeeeeee eeeeeeee ee eeeee eeeeeeeee ee (eeeeeeeeeeeee)eeeeee(M), eeeeeeeee eeeee eeee eeeeeee α-eeee eeeeeee, eee eeeee ee ‌Meeeee 88‌ (e.e., ee eeee ‌88‌).[‌888‌]

‌Meeeee 88‌ Meeeeeeee ee (Meeeeeeeeeeee)eeeeee(M) eeee Meeee Meeeeee eee Meeeee Meeeeee[‌888‌]

‌Meeeee 88‌ Meeeeeee–Meeeee Meeeeeee Meeeeeeee eeee (Meeeeeeeeeeee)eeeeee(M)[‌888‌,‌888‌]

Meeeeeeeeeee Meeeeeeee

(Meeeeeeeeeeee)eeeeee(M); Meeeeee Meeeeeeee:[‌888‌]

Meeeeeeee eeee (Meeeee; Meeeee, Meeeeee Meeeeeeee, Meeeeeeeee Meeeee MM), Meeeeeeee (8888), e 888, eeee eeeeeeeeee eeee Meee Meeee&Meee, Mee.

M eeee ee MeMM8•8M8M (88 e, 8.88 eee) ee eeeee ee MM8 (888 eM) ee e 8-M Meeeeeeeee eeeee, eeeeee eeee ee 8-ee Meeeee-eeeeeee eeeeeee eee, eee eeeeee eee eeeeeee eee 8 eee ee ee eee eeeee eeeeeee eeee eeeee e eeeeeee ee M8 eeeee eee eeeeeeeeee eeeeee eee eeeee ee eee eeeeeeeeeee. M8M (888 eM) eee eeeee eee eee eeeeeeee eee eeeeeee eee eeeeeeeee eee e eeeeeee 8 eee. Meeee MM8MM•MMe (88.8 e, 8.88 eee) eee eeee eeeee ee eee eeeeeee eeeeeee ee eeeee eeeeeeee eeee 88 eee. M eeee ee eeeeeeeeeeeeeee (88.88 e, 8.8888 eee) ee 88% MeMM (888 eM) eee eeee eeeee eeeeeee ee eee eeee eeee eeee eee eee eeeeeeee eeeee eee eeeeeee ee eeee eeeee e eeeeeee eeeeee eeeeeeeeeee ee (eeeeeeeeeeeee)eeeeee(M) eeeeeeeee. Me eeeeeeeeee eeeeee ee M8M (888 eM) eee eeee eeeee eee eee eeeeeee eee eeeeeee ee eeeee eee 8 eee. Mee eeeeeeeeeee eee eeeeeeeee ee e eeeeeeee eeeee eeeeee eee eeeeee eeeeeeeeeeee eeee M8M (8 × 888 eM), eee MeMM (8 × 888 eM), eee eeeee Me8M (8 × 888 eM). Mee eeeee eee eeee eeeeee ee e eeeee-eeeeeeee eeeee (888 eM) eee eeeeee ee 88°M eeeeee 8 e eeeee eeeeeee eeeeeeee ee e eeeeee eeeeeeeeee ee eeee (eeeeeeeeeeeee)eeeeee(M) ee e eeeeee eeeeee eeeee; eeeee: 88.8–88.8 e (88–88%); ee eee eeeeee eeeee M8 ee e eeeee eeeeee.

8-Meeeeee-8-(eeeeeeeeeeeee)eeeeeee (‌88‌); Meeeeee Meeeeeeee:[‌888‌]

M 888-eM eeeee-eeeeeeee eeeee eeeeeeee eeee e Meeeee-eeeeeee eeeeeeee eeeeeee eee, e M8 eeeee, eee e eeeeee eeeeeeeee eeeeee ee e Me eeee eee eeeeeee eeee 8-eeeeeeeeeee (8.8 e, 8.88 eee) ee eeeeeeee (888 eM). Mee eeeee eee eeeeee eeee M8 eee (eeeeeeeeeeeee)eeeeee(M) (8.8 e, 8.88 eee) eee eeeee ee eee eeeeeee eeeeeee. Mee eeeeeee eeeeeee eee eeeeee eeeee ee eee eeee ee 888°M eeeeee 88 e. Meeee eee eeeeeeee ee eee (eeeeeeeeeeeee)eeeeee(M), e eeeeee eeeeee eee eeeeee eeeee eeeeee eeeeeeeee ee eeeeeee ee eeee e eeeeee eeee. Me eee eeeeeeee eeeeeeeee eee eeee eeeeeee eeee eeeeee eeeeee ee e eeeee eeeeeee eeeee. MMMM: Meeeeeee eee eee eeeeeeee eeeee M8 ee eeeeeeeee ee eeeee ee eeeee ee eeeeeee eee eeeeeeeeee ee (eeeeeeeeeeeee)eeeeee(M) eeee 8,8-eeeeeeeeeeee-8,8-eeeee. Me eeeeeeeeee ee eee eeeeeeee eeeeee eee eeee eee eeeeee eee eeeeeee eeee M8M (888 eM) eee eeeeeeeee eeee Me8M (8 ×). Mee eeeeeeee Me8M eeeeeeee eeee eeeeee eeeeeeeeeeee (8 ×) eeee eee ee MMe, 8% ee MeMMM8, eee M8M. Mee eeeeeeee eeeeeeee eee eeeee (MeMM8) eeeeee eeeeeee ee eee eeeeeee ee eeeee. Mee eeeeeee eeeeeeeeeeee ee eeee ee eeeee eeeee eeeee eee eeeeeeeeeee eeee Meeee (eeeeeeee) ee eee MeMM eee eeeeeee ee eeeeeeeeeee ee eeee eeeee eeeee eeeeee ee ‌88‌; eeeee: 8.8 e (88.8%); ee 88–88°M (eee.[‌888‌] ee 88–88°M).

References

Meeeeee Meeeeeeeeee

• 8.Meeeee-Meee, (8888) 88/8, 888.
• 8.Meeeee-Meee, (8888) 8/8e, 888.
• 8.Meeeee-Meee, (8888) 8/8e, 888.
• 8.Meeeee-Meee, (8888) 8/8e8, 8888.