Cumulenes synthesis

Binuclear cumulenes, synthesis, 230 Bis(methylene)propenylphosphorane, synthesis with phosphaalkenes, 19 [ ( -BuSe)Fe2(CO)6h(/i4-Se)], synthesis and structure, 275, 276 Butene 1,4-diones, synthesis, 224... 

Cumulene synthesis. A second synthetic sequence developed by Arens et al.m is illustrated by the synthesis of 1 -methoxy-4-methyl-1,2,3 -pentatriene (5). 

One of the most versatile methods for the synthesis of derivatives with the acetylene or cumulene system consists In deprotonatlon of the starting acetylene or cumulene and subsequent reaction of the anionic or organometal1ic intermediate with an electrophilic reagent. 

Treatment of geminal dihalocyclopropyl compounds with a strong base such as butyl lithium has been for several years the most versatile method for cumulenes. The dihalo compounds are easily obtained by addition of dihalocarbenes to double--bond systems If the dihalocyclopropanes are reacted at low temperatures with alkyllithium, a cyclopropane carbenoid is formed, which in general decomposes above -40 to -50°C to afford the cumulene. Although at present a number of alternative methods are available , the above-mentioned synthesis is the only suitable one for cyclic cumulenes [e.g. 1,2-cyclononadiene and 1,2,3-cyclodecatriene] and substituted non-cyclic cumulenes [e.g. (CH3)2C=C=C=C(CH3)2]. 

The cyclodimerization of 82 to 83 is an example of a Ni(0)-mediated synthesis of [4]radialenes from [n]cumulenes. Applications of this method to butatriene derivatives 9050,63, 9164 and 9365,66 are shown in Scheme 10. The usefulness of Ni(0) catalysis for this transformation was first demonstrated by West and coworkers63 and later explored in detail by Iyoda and coworkers42,54,67. In some cases, Ni(0) catalysis improves the... 

G. M. Coppola, Allenes in Organic Synthesis, Wiley New York, 1984 (f) D. J. Pasto, Tetrahedron, 1984,40, 2805-2827 (g) L. Brandsma, Synthesis of Acetylenes, Menes and Cumulenes Elsevier Oxford, 2004. 

Synthesis of Acetylenes, Allenes and Cumulenes A Laboratory Manual by L. Brandsma and H.D. Verkruijsse... 

Phenylmethylsilanediol, synthesis, 42 155 Phenylsilanetriol, monosodium salts, 42 169 4 -Phenyl-2,2 6, 2 -terpyridine bis nickel complex, 30 74 molecular structure, 30 74 PhjtfluorenyllSiOH, 42 197 (Ph(Me2N)C-=Nli], 37 59-65 orientation of imino ligand, 37 61-63 (PhMe SiljCSiH OH, 42 244-245, 248 (PhMe SiljCsiMeHlOH), 42 191 Phosphaalkenes acyclic, 33 338-353 butadienes, 33 346-349 cumulenes, 33 352... 

Synthesis of strained heterobicycles from alkynes and hetero-cumulenes. " ... 

Cyclodimerization of unsymmetrically substituted butatricncs such as 12 give both head-to-head and hcad-to-tail cycloaddition products. The structure of the head-to-head dimer was confirmed by its independent synthesis from the mixed cycloaddition of cumulenes 8 and 10,21 22 These dimerizations proceed by discrete nickel cyclopentanes which was established by the isolation of the 2-bispyridinenickel complex of the l.l,4,4-tetramelhylbuta-l,2,3-triene dimer.23 4-Radialenes with extended conjugation, potential organic conductors and semiconductors, have been prepared by similar methods as illustrated by the examples below.24,25... 

The conversion of dihalocyclopropane to allene can be extended to the synthesis of cumulenes by repeating the sequence, as illustrated by the synthesis of 1,2,3-cyclononatriene (Scheme 7).161... 

Brandsma, L. Verkruijsse, H. D. "Synthesis of Acetylenes, Allenes, and Cumulenes A Laboratory Manual" Elsevier New York, 1981 p. 55. 

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