1,3-Diacetylenes rearrangement

The reaction of diacetylene and its asymmetric homologs (penta-l,3-diyne, hexa-1,3-diyne) with semicarbazide (72ZOR2605) affords the amides of 3-methyl-pyrazole- 1-carboxylic acid (27) (80°C, EtONa, EtOH, 40 h). Amide 26 undergoes irreversible rearrangement to amide 27 at 80°C (EtONa, EtOH). 

Organoboration of diacetylenic derivatives proceeds stepwise and in a number of cases is also accompanied by 1,2-anionotropic rearrangement giving rise to polycyclic compounds (see Section 12.13.4.2) <2001CEJ775, 2002CEJ1537>. 

Only two general methods have been developed for the synthesis of the macrocyclic annulenes.9 The first of these, developed by Sondheimer and co-workers, involves the oxidative coupling of a suitable terminal diacetylene to a macrocyclic polyacetylene of required ring size, using typically cupric acetate in pyridine. The cyclic compound is then transformed to a dehydroannulene, usually by prototropic rearrangement effected by potassium i-butoxide. Finally, partial catalytic hydrogenation of the triple bonds to double bonds leads to the annulene. 

Radiolysis of the diacetylene hexa-l,5-diyne (50) generates the hexa-1,2,4,5-tetraene radical cation (51 +) via a Cope rearrangement in the Freon matrix. ... 

Rearrangement of Disubstituted Amino Diacetylenic Tertiary Alcohols to Ynamines [12]... 

With cyanoacetylene (70JAP33890) and diacetylene (76ZOR905, 80IZV2803), oximes give the 0-vinyl derivatives 152 which, however, could not be rearranged to pyrroles (see Section V.B). 

In the reaction of amidoximes 153 with diacetylene in the presence of KOH in aqueous DMSO, the 0-adducts 156 are formed (Scheme 78) no rearrangement thereof to ethynylimidazoles has been observed (76-IZV1430). 

Four types of intermediates may be postulated for these rearrangements, viz. a tetraene, two dienynes and a skipped diacetylene, as shown in Scheme 8 . The available evidence indicates that the interconversions occur by a carbanionic mechanism. Substantial build-up of intermediates is not observed in most of these reactions, and the relative importance of the routes has not been established. 

An interesting rearrangement occurs during the alkaline decomposition of quaternary salts of Mannich bases derived from diacetylenes - When it is heated with KOH, the salt 307 gives 1-hexene-3,5-diyne (309) in high yield, presumably by initial 1,6-elimination followed by rearrangement of the pentaene 308. 

Besides processes (1) and (2), the reader should be aware that nucleophilic attacks on alkynes are treated in other chapters of this book, dealing with rearrangements, cyclizations, polyacetylenes, cyclic acetylenes and perhaps others. A number of publications overlap with ours in different ways and at different levels -. They treat individual alkynes or families " , e.g. acetylene, diacetylenes , acetylene dicarboxylic esters haloacetylenes , alkynyl ethers and thioethers > ynamines , fluoro-alkynes ethynyl ketpnes , nitroalkynes , etc. synthetic targets, e.g. pyrazoles , if-l,2,3-triazoles , isothiazoles , indolizines S etc. reagents, e.g. nitrones , lithium aluminium hydride , heterocyclic A -oxides - , azomethine ylids - , tertiary phosphorus compounds , miscellaneous dipolar nucleophiles - , etc. The reader will appreciate that all of these constitute alternate entries into our subject. 

Isomerization of unsaturated compounds. Raphael reported the finding that a 10% solution of the reagent in refluxing diethylene glycol dimethyl ether (b.p. 161°) rearranges diacetylenes to aromatic hydrocarbons in yields of about 65%. Thus 1,6-heptadiyne affords toluene. 

The low reactivity of 2 towards C-C double bonds is also seen in the reaction with a diacetylene linked by a C-C double bond. Again it can be assumed that the reaction sequence is initiated by a four-fold cycloaddition of four molecules of 2 followed by a rearrangement to furnish the two disilabicyclohexadiene units linked by a C-C double bond 10 (Eq. 4). In both molecules the C-C double bonds adopt an all-frans arrangement [6]. These compounds behave like polyacetylenes, where the dlX-trans form is more stable then the all-cis configuration [7]. 

Following an isolated report in 1980, it has now been shown that the rearrangement of diacetylenic diamines (210), via their lithio-derivatives, into conjugated triene-diamines (211), is a general process. However, some examples rearrange only very slowly. ... 

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