Double bond systems

For vicinally disubstituted olefins (and similar double-bond systems) the traditional prefixes cis and trans can be retained, although for all higher substituted systems the descriptors (Z) and ( ) as defined on the basis of the CIP sequence rules must be applied. 

2-frans,4-cis-Hexa-2,4-dienoic acid (2Ey 4Z)-Hexa-2,4-dienoic acid 

If in the above example the conformation relative to the 3,4-single bond should also be specified, the supplemental prefixes s-cis (vs. s-trans) will serve that purpose, thus giving s-frans,(2E,4Z)-hexadienoic acid. 

Lithium naphthalen-2-yl-( )-diazenolate trad, Lithium naphthalene-2-a f/-diazoate 

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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]. 

Under favorable conditions, low molecular weight organics may polymerize on surface of adsorbent (dialkenes, 1-alkenes, alkynes, conjugated double-bond systems, and epoxides are especially susceptible to this behavior). 

Conjugated double bond systems usually undergo 1,4-addition. 

Free radical (3) can rearrange, add oxygen to form a peroxy free radical, abstract a hydrogen from a methylene group between double bonds, combine with another free radical, or add to a conjugated double-bond system. 

The concept of a 1,5-dipolar cyclization gives rise to a general method for the synthesis of an appreciable number of heterocyclic systems. 1,5-Dipoles are derived from 1,3-dipoles by conjugation with different double bond systems, and it is possible to derive 98 theoretically possible 1,5-dipolar systems. The general expression for a 1,5-dipole and some possible combinations of double bond systems are shown in Scheme 14. 

Antimony(III) chloride forms colored 7t-complexes with double bond systems (e.g. vitamin A). 

Nakazaki, M., Yamamoto, K., and Naemura, K. Stereochemistry of Twisted Double Bond Systems, 125, 1-25 (1984). 

Matsumoto et al. reported some reactions of diruthenium complexes containing a bridging disulfide ligand with unsaturated compounds such as olefins and ketones [135]. These diruthenium complexes show unique reactivities towards double-bond systems since the S-S bond has some double bond character from the contribution of the canonical structure B in Scheme 36. 

By homogeneous reaction of the conjugated double bond system selectively the C=C double bond is hydrogenated [63-66] the ester function is not affected. Moreover, by action of the chiral catalyst, a chiral hydrogenated product is created with good enantioselectivity. 

The discussion of the activation of bonds containing a group 15 element is continued in chapter five. D.K. Wicht and D.S. Glueck discuss the addition of phosphines, R2P-H, phosphites, (R0)2P(=0)H, and phosphine oxides R2P(=0)H to unsaturated substrates. Although the addition of P-H bonds can be sometimes achieved directly, the transition metal-catalyzed reaction is usually faster and may proceed with a different stereochemistry. As in hydrosilylations, palladium and platinum complexes are frequently employed as catalyst precursors for P-H additions to unsaturated hydrocarbons, but (chiral) lanthanide complexes were used with great success for the (enantioselective) addition to heteropolar double bond systems, such as aldehydes and imines whereby pharmaceutically valuable a-hydroxy or a-amino phosphonates were obtained efficiently. 

Fluoran compounds having an 7V-alkyl-/V-arylamino group at 3 -position such as 2 -chloro-6 -(7V-ethyl-4-methylanilino)fluoran (26 R1 = CH3, R2 = H, R3 = Cl),22 6 -((V-ethyl-4-methylanilino)-2 -methoxyfluoran (26 R1 = CH3, R2 = H, R3 = CH30),22 and 6 -(4-chloro-(V-ethylanilino)-2, 3 -dimethylfluoran (26 R1 = Cl, R2, R3 = CH3)22 also develop vermilion color, but these color tones are more bathochromic because of longer conjugated double bond system. 

If the arylamino group is substituted with an appropriate group to extend the conjugated double bond system, blue color can also be obtained. For example, 10 -(4-anilinoanilino)benzo[c]fluoran (32 R = C6H5NH)24 and 10 -(4-styrylanilino)benzo[c]fluoran (32 R = C6H5CH=CH)25 develop blue color. 

Extension of conjugated double bond system at 2 - and/or 6 -positions makes it possible for fluoran compounds to have an absorption in the near infrared region up to 1200 nm. These include 2 -anilino-6-(4-anilinoanilino)-3 -methylfluoran (62),63 6 -[4-(4-anilinoanilino)anilino]-2 -chloro-3 -methylfluoran (63),7 6 -[4-(4-dimethylaminoanilino)anilino]-2 -methylflu-... 

Substituted cyclobutanes or benzene rings are formed by the reaction of imidazolides with suitable double-bond systems. 

The radical-induced cleavage of a,/ -aziridino alcohols proceeds in analogy to that of a,/ -epoxyalcohols, leading regiospecifically to allyl amines (a). By successive reactions with double bond systems, pyrrolidines are formed (b) [68]... 

Because the aziridine part of such a molecule can be obtained easily from a double bond system, these reactions constitute a method for converting allyl alcohols into allyl amines via aziridination. 

Cycloalkanes can be synthesized from alcohols containing double-bond systems. 

In contrast to the numerous reactions involving single bonds, interactions of stannylenes with double bonds have not extensively been studied. There are only two cases known where addition of a monomolecular stable stannylene to a double bond system takes place (Eqs. (31) 154) and (32)133) see also Ref.169)... 

A. Double Bond Systems Containing a Silicon Atom. 127... 

In addition to the telluration of a silylene, another unique synthetic route has been developed for the silicon-tellurium double bond system. Recently, it has been reported that the exhaustive reduction of an overcrowded dibromosilane Tbt(Dip)SiBr2 (61) with an excess amount (more than 4 equiv.) of lithium... 

Although some examples of thermodynamically stabilized double bond systems between Group 14 and Group 16 elements showed trigonal planar geometry due to their structural restriction, almost all of their bond lengths are longer than those kinetically stabilized and theoretically predicted.67 These results clearly show that considerable electronic perturbation is inevitably involved in the thermodynamically stabilized systems. 

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