Rearrangements acetylene-allene

Triple-bond compounds react with carbenes to give cyclopropenes, except that in the case of acetylene itself, the cyclopropenes first formed cannot be isolated because they rearrange to allenes. Cyclopropenones (p. 58) are obtained by hydrolysis of dihalocyclopropenes. ... 

Alkadiene- and alkatrienephosphonates are available from acetylene-allene rearrangement of acetylene phosphites which could easily be prepared from the reaction of carbonyl compounds and 1-alkynes. 

Petrov and coworkers [41] showed that the reaction of dibromides of alkenephos-phonic acids with acetylenic alcohols involved an acetylene-allene rearrangement. The products so formed hydrolyzed easily to the corresponding phosphinic acids. The latter on heterocyclization afforded 2,5-dihydro-l,2-oxaphosphole-2-oxide derivatives (Scheme 11). 

Boisselle, A.P. and Meinhardt, N.A., Acetylene-allene rearrangement reactions of trivalent phosphorus chlorides with a-acetylenic alcohols and glycols,. Org. Chem., 27, 1828, 1962. 

Cutting and Parsons described the transformation of acetylenic alcohols 314 into allenyl phenyl thioethers 316 by a two-step procedure (Scheme 8.85) [174], Deprotonation of alkynes 314 with n-butyllithium is followed by addition of phenylsulfenyl chloride, forming sulfenyloxy intermediates which subsequently rearrange to allenic sulfoxides 315. Treatment of allenes 315 with methyllithium results in loss of the sulfoxide moiety to form allenyl sulfides 316 in reasonable yields. 

Investigations of base-catalyzed isomerizations of allene derivatives have been recently continued. For instance, the rearrangement of allene ethers 53 under superbasic conditions (KOH-DMSO) is considered as one of the steps in hydration of acetylene derivatives (equation 17)31,32. 

The various types of acetylene-allene rearrangements [la, 38-41] have been described by Jacobs [38] to involve the following processes ... 

The Acetylene-Allene Rearrangement. In Section 4.2.2 we discussed the base-catalyzed acetylene-allene transformation. In a study by Kitagawa et al. a useful... 

In the course of investigations on allylic and acetylene-allene rearrangements of 3-substituted quinuclidines, it was found that by oxidation and ozonolysis of compounds with functional groups at positions allylic to the double bond, not only the double bonds but also the adjacent carbon-carbon bonds are broken. For example, in the oxidation of 3-hydroxy-3-vinylquinuclidine (119), with potassium permanganate under mild conditions, and in its ozonolysis, qui-nuclidin-3-one (2) is formed along with 3-hydroxy quinuclidine-3-carboxylic acid.161 The positions of double bonds in such systems can be firmly established by NMR spectroscopy, but not by oxidative methods.101... 

These -propargyl rhenium complexes undergo kinetic addition of nucleophiles at the central C atom to produce rhenacyclobutenes. The nucleophiles range from PR3 to malonate, acetylides, pyridines, and water. The derivatives of the addition of pyridines, however, are unstable and undergo further rearrangements to allene or acetylene complexes. Protonation of the metaUacyclobutenes produces u -allyl complexes. 

The method has been extended to the preparation of difunctional compounds. Dihalides Including the mixed variety are formed in 90 to 98% yields. Primary unsaturated bromides of the type RCH=CHCH,Br have been formed from the corresponding alcohols by the action of phosphorus tribromide and pyridine at a low temperature without any apparent rearrangement. However, the corresponding secondary-carbinol system, RCHOHCH=CH is very susceptible to allylic isomerization. The formation of a, -acetylenic bromides from acetylenic alcohols and phosphorus tribromide is common (40-70%). An acetylenic-allenic isomerization has been observed, viz.,... 

In the following steps (eq 7), we observed two HCl-catalyzed processes an acetylenic-allene rearrangement (to 10) and an allenic-acetylene rearrangement (to 11). While both 10 and 11 were easily identified by their characteristic NMR signals and could be distilled as a mixture without decomposition, only the final acetylene derivative (11) could be isolated in pure form after fractional distillation. Propargyl bromide reacted similarly with the three-coordinate phosphine, but in this case all of the chemical transformations occurred very rapidly and only the final acetylene phosphoranimine (11) could be isolated. 

We also obtained interesting results in studying the reactivity of acetylenic alcohols with the two-coordinate phosphines (eq 9). Depending on the position of the OH group relative to the triple bond, different types of products are obtained. In all cases, however, the first step of the reaction is addition of the 0-H group to the P=N center to yield the three-coordinate phosphine. In the case of a-acetylenic alcohols, this addition is followed by a rapid acetylene-allene rearrangement and a... 

Pudovik. A.N.. and Aladzheva, I.M., Acetylene-allene-acetylenic rearrangements of phosphites with a p.y-acetylene linkage in the ester radical, Zh. Obshch. Khim., 33, 707, 1963 J. Gen. Chem. USSR (Engl. Transl.). 33. 700. 1963. 

Precursors for an allene oxy-Cope variant are readily prepared from acetylenic derivatives. Rearrangement of allenic alcohol 11 yields a 1 1 EjZ mixture of 121108. 

An acetylene-allene rearrangement has been postulated as a mechanism for this reaction. The diol (55) underwent acid-catalyzed cyclization to give the di-hydrofuran derivative (56) (Chernysh et aL, 1977). 

Propargylic sulphonium salts (239) on treatment with base rearrange to allenic thioethers (240) a competitive reaction is isomerization of the acetylene to the allene sulphonium salt (241) followed by an analogous sigmatropic rearrangement to the acetylenic thioether (242). There is no isomerization of (240) to (242) under the reaction conditions. ... 

The isomerization of acetylenic oxiranes cis- and trows-91 to allenic ketone 94 has recently been described (Scheme 5.18). It is proposed that the rearrangement proceeds via a dilithium ynenolate [33]. 

The facile thermal decomposition of the dimethyl and diethyl derivatives of (II) to nitrogen and carbene intermediates is emphasized by the readily discernible correlations between the reactant and product orbitals. On the other hand, the greater delocalization of the molecular orbitals of (I) may be a factor in its preference to rearrange, without decomposition, to methyl acetylene and allene. 

Rearrangement of acetylenic sulphenates to the allenic sulphoxides 151 was discovered when the synthesis of propargylic ester of trichloromethanesulphenic acid 152 was attempted (equation 86). This reaction is of general scope and gives very good yields of allenic sulphoxides (Table 14) from structurally diverse cohols and various sulphenyl chlorides Reaction of alkynols 153 with benzenesulphenyl chloride in the presence... 

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