Alkynes rearrangements with

O-Vinyl oximes prepared from oximes and activated alkynes rearrange with gold catalysis to substituted pyrroles (Scheme 126). °... 

The ester/alkyne rearrangement system can be extended by conjugation to involve a more distant site. The reaction of diethyl phosphorochloridate with 3-methylhex-4-yne-2-ene-l-ol leads to the vinylogous propargylic ester rearrangement as shown in Equation 4.39.176... 

The isomerization of the smallest alkynes 80 with halogens in a propargylic position has been described for chlorine [151, 152], bromine [153] and iodine [154] (Scheme 1.35), but often might proceed by an SN2 -type substitution rather than a prototropic rearrangement [155-159]. On the other hand, transformations such as 82 —> 83 [160] or 84 —> 85 [161] are clearly prototropic (Scheme 1.36). This is also true for propargylic halides such as 86 with its additional ester group assisting the prototropic isomerization [162,163] (Scheme 1.37). 

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. 

Since tautomeric rearrangement is not possible when secondary amines react with acetylene, the intermediate enamines can be isolated.312,314 Vinylation with acetylene of heterocyclic nitrogen bases, such as pyrrole, indole, carbazole, was achieved in this way.312,315 However, when terminal alkynes react with secondary amines,... 

Alkylbromoborancs (1) can also be used to provide frans-alkenes by hydroboration of a 1-bromo- 1-alkyne. The adducts rearrange with sodium methoxide to (trans-l-alkyl-l-alkcnyl)boronate esters (3), which can be converted into either tran.v-alkenes (4)or ketones (5), as shown inequation III.7... 

To our knowledge there is no example in the literature of a stable alkene (or alkyne) complex with magnesium as central atom, n Complexes have, however, been postulated as intermediates in the rearrangement reactions of some alkenyl Grignard reagents (86). 

Alkenes, perfluoro-cycloadditions to benzyl azide, 60, 35 pyridine imines and ylids, 60, 36 Alkenes, perfluoro-, as heterocyclic precursors, 59, 10 Alkylation, free-radical, of 1,3-dimethyluracil, 55, 227 A-Alkylation, [ 1,2,4]triazolo[ 1,5-u)-pyrimidines, 57, 110 Alkynes, photocycloaddition to uracils, rearrangement with HCNO elimination, 55, 149 Alkynes, ethoxy-, cyclaoddition to hexafluoroacetone azine, 60, 32 Alkynes, perfluoro-, as heterocyclic precursors, 59, 10 Allenes... 

Dithioles 480 undergo cycloaddition with alkynes, and subsequent rearrangement with loss of CI2 gives IH-thieno[2,3-f]thiopyran-7-thiones 481 and 4//-thieno[3,2-f]thiopyran-4-thiones 482 as an isomeric mixture (Scheme 80) <20050L791>. 

In the hydrogenolysis of acetylenic Mannich bases, rearrangement with double bond migration, accompanying the elimination of the amine, may take place with formation of an alicne derivative instead of the expected methyl alkyne. 

The heterometallacyclic alkyne-containing complex 85 (M = Mo or W, R = Pr or /7-MeQH4, R = Me or Ph) isomerizes into 86 above 20°C (90). At 55°C the tungsten compound with R being Pr and R Ph rearranges, with incorporation of the alkyne ligand into a metallacycle and extrusion of the thiolate from the chelate ring, to form 87. 

In general, synthesis of 4-isoxazolines is accomplished via three routes 1,3-dipolar cycloaddition of nitrones to alkynes or by the oximation of a,i -ethylenic ketones, a-alkynic ketones and aldehydes or from the selective reduction of isoxazolium salts. The nitrone (262) underwent tandem cyclo-addition-[2,3]sigmatropic rearrangement with allenyl sulfoxide (263). And it resulted in 4-isoxazoline (264) (Equation (46)) <89TL663>. 

The addition of monochlorocarbenes to phospha-alkynes results initially in the formation of the transient 2H-phosphirenes (231), which then undergo rearrangement, with migration of chlorine from carbon to phosphorus, to give the stable P-halo-lH-phosphirenes (232). Unlike their nitrogen analogues, the latter cannot... 

Some alkyne systems, with comparatively labile bonds, undergo rearrangement processes. Thus photorearrangement of the silylacetylene 152 1,3-silyl migration affording the allene 153. ... 

Tin alkynes rearrange to yield allene products in much the same way as do lithium alkynes, except that the reaction involves a radical mechanism. It is very similar to the reaction of allyl stannanes with alkyl halides, which substitutes the allyl group. Similar reactions are reported for allyl derivatives of cobalt, rhodium and iridium, but this work has not been extended to alkyne derivatives. 

Pal, R., Clark, R. J., Manoharan, M., Alabugin, 1. V. (2010). Fast Oxy-Cope Rearrangements of Bis-alkynes Competition with Central C-C Bond Fragmentation and Incorporation in Tunable Cascades Diverging from a Common Bis-allenic Intermediate. The Journal of Organic Chemistry, 75(24), 8689-8692. 

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