Cyclohexane alkenyl

To a solution of 1.30 g (5.5 mmol) of (-)-sparteine in 20 mL of pentane and 2.5 mL of cyclohexane are sequentially added dropwise between —78, C and -70 C 5.5 mmol of an approx. 1.5 M solution of sec-butyllithium in 2-methylbutane/cyclohexane and 5.0 mmol of the 2-alkenyl diisopropylcarbamate in 5 mL of pentane. After 10 min stirring, the flask is raised from the dry-ice/acetone bath and cautiously shaken to remove the precipitate from the glass wall of the flask. The temperature must not rise above — 50 CC. After chilling the flask again to —70 °C, shaking of the flask is repealed and stirring is continued below — 70 C overnight. 

Apart from the alkenyl succinic anhydrides, other cyclic anhydrides are solids, requiring the use of a delivery solvent, or a solid-state reaction. Apart from succinic anhydride, phthalic (PA) (Figure 4.2a) (Risi and Arseneau, 1958) and maleic anhydride (MA) have also been extensively studied (Figure 4.2b) (Clemons etal., 1992). Goethals and Stevens (1994) have reported reaction of wood with glutaric (Figure 4.2c) or cyclohexane-1,2-dicarboxylic anhydride (Figure 4.2d) and subsequent reaction with epichlorohydrin. 

Fig. 12 Illustration of the chemistry employed for preparation of a modified Si(lll) surface. Firstly, a layer of alkenyl acid is bound to the surface by covalent attachment. Secondly, a layer of polylysine is electrostatically bound to the carboxylic activated surface and finally the DNA is bound to the surface in a reaction mediated by sulfosuccinimidyl 4-(N-maleimidomethyl)-cyclohexane-l-carboxylate [27]...

Alkenyl nitrones, having the alkene connected to the nitrone nitrogen atom, have been used in another approach to intramolecular reactions (231-235). Holmes and co-workers have this method for the synthesis of the alkaloid (—)-indolizidine 209B 137 (210,231). The alkenyl nitrone 134, was obtained from the chiral hydroxylamine 133 and an aldehyde. In the intramolecular 1,3-dipolar cycloaddition, 135 was formed as the only isomer (Scheme 12.45). The diastereofacial selectivity was controlled by the favored conformation of the cyclohexane-like transition state in which the pentyl group was in a pseudoequatorial position, as indicated by 134. Further transformation of 135 led to the desired product 137. 

Tamao and Ito proposed a mechanism for the nickel-catalyzed cyclization/hydrosilylation of 1,7-diynes initiated by oxidative addition of the silane to an Ni(0) species to form an Ni(ii) silyl hydride complex. Gomplexation of the diyne could then form the nickel(ii) diyne complex la (Scheme 1). Silylmetallation of the less-substituted G=C bond of la, followed by intramolecular / -migratory insertion of the coordinated G=G bond into the Ni-G bond of alkenyl alkyne intermediate Ila, could form dienylnickel hydride intermediate Ilia. Sequential G-H reductive elimination and Si-H oxidative addition would release the silylated dialkylidene cyclohexane and regenerate the silylnickel hydride catalyst (Scheme 1). 

Lanthanide-catalyzed enyne cyclization/hydrosilylation was also applied to the synthesis of silylated alkylidene cyclohexane derivatives. For example, reaction of the 3-silyloxy-l,7-enyne 17 with methylphenylsilane catalyzed by Gp 2YMe(THF) at 50°G for 8h gave 18 in quantitative yield as a 4 1 mixture of trans cis isomers (Equation (11)). Employment of methylphenylsilane in place of phenylsilane was required to inhibit silylation of the initially formed yttrium alkenyl complex, prior to intramolecular carbometallation (see Scheme 8). 

Cracking and disproportionation in the reaction of hexane could be suppressed by the addition of cycloalkanes (cyclohexane, methylcyclopentane, cyclopentane).101 Furthermore, 3-methylpentane and methylcyclopentane also reduced the induction period. These data indicate that reactions are initiated by an oxidative formation of alkene intermediates. These maybe transformed into alkenyl cations, which undergo cracking and disproportionation. When there is intensive contact between the phases ensuring effective hydride transfer, protonated alkenes give isomerization products. 

In the field of hydrocarbon conversions, N. D. Zelinskii and his numerous co-workers have published much important information since 1911. Zelinskii s method for the selective dehydrogenation of cyclohexanes over platinum and palladium was first applied to analytical work (155,351,438,439), but in recent years attempts have been made to use it industrially for the manufacture of aromatics from the cyclohexanes contained in petroleum. In addition, nickel on alumina was used for this purpose by V. I. Komarewsky in 1924 (444) and subsequently by N. I. Shuikin (454,455,456). Hydrogen disproportionation of cyclohexenes over platinum or palladium discovered by N. D. Zelinskii (331,387) is a related field of research. Studies of hydrogen disproportionation are being continued, and their application is being extended to compounds such as alkenyl cyclohexanes. The dehydrocyclization of paraffins was reported by this institute (Kazanskil and Plate) simultaneously with B. L. Moldavskil and co-workers and with Karzhev (1937). The catalysts employed by this school have also been tested for the desulfurization of petroleum and shale oil fractions by hydrogenation under atmospheric pressure. Substantial sulfur removal was achieved by the use of platinum and nickel on alumina (392). 

Table 3.15 Transition temperatures (°C) for some tT ns-l-alkenyl-4-(4-cyano-phenyl)cyclohexanes (74 and 129-139)...

Finally, when aziridines bear a 2-alkenyl substituent, they can engage in an SN2 reaction with dialkylzinc reagents using copper catalysts. Enantioselectivity can also be induced by including a chiral ligand, such as the binaphthyl phosphoramidite 174. For example, the aziridinyl cyclohexane 175 provided exclusively the trans-, 4 adduct with 83% ee upon treatment with dimethylzinc in the presence of copper(II) triflate and ligand 174 <03TL8559>. 

Bicyclol5.3.0 decan 8-Methylen-2-oxo- E21d, 3607 [2-(l-Alkenyl)-1 -etheny 1-1 -OH — cyclohexan ... 

The intramolecular aziridination of 2-(alkenyl)phenyl azides was best performed under pho-tolytic conditions116-117, generating the nitrene (ca. 0.001 M solution in cyclohexane, 350 nra, Rayonet Photoreactor)118. The nitrene addition reaction proceeded with complete diastereose-lectivity, the double bond geometry was retained in the aziridine thus produced. The alkaloid ( )-virantmycin was synthesized from the aziridine 2117. 

Allyl-(2-subst.-l-alkenyl)-sulfan l,9g (0,03 mmol) 2-Butyl-lithium in Cyclohexan gibt man langsam bei 78° zu einer Losung von 6,7 g (0,03 mmol) Allylthio-methanphosphonsaure-dimethylester in THF. Bei -78° werden 2,9g (0,03 mmol) Cyclohexanon zugegeben anschlieBend wird 15 Min. auf 25° und 15 Stdn. auf 50° er-warmt Ausbeute 4,2 g (83°/o). 

Allyl-1-formyl-cyclohexan 5,0 g (0,03 mmol) Allyl-(2-subst.-l-alkenyl)-sulfan und 10,8 g (0,05 mmol) Quecksilber(II)-oxid werden 10 Min. auf 190° erhitzt. Es wird vom schwarzen Riickstand abdestilliert Ausbeute 3,7 g (82%) Schmp. (2,4-Dinitro-phenylhydrazon) 153-154°. 

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