Adduct, cis-

An intermediate of the metallation procedure, the adduct cis-PtCl2H2-(Hemato-XI), has been characterized [86c]. Tetrabenzporphyrin was transformed into its Pd and Pt complexes, Pd(TBP) or Pt(TBP), with PdCl2 in DMF [87]. 

Reaction of dichloroketene with cis or trans cyclo-octene suggests that it is a concerted reaction each gives stereospecifically a different stereoisomer of the adduct cis-15 gives cis- 16 while trans-17 gives trans-18. The marked hydrogen atoms should make this clear. The very reactive trans -cyclo-octene 17 gives a 100% yield so there is no room for any 16 in the product.3... 

Adducts (cis-1 bis-adducts) of C6o are C -symmetric and have a noninherently chiral addition pattern under the condition that there is a difference between the residues attached to C(l) and C(4), or to C(2) and C(3) (Figure 1.37). This situation is realized in the [60]fullerene derivative ( )-159 (Figure 1.37), which was obtained from ethyl azidoformate addition... 

Alcock and coworkers studied the polymerization of butadiene (as well as of monoolefins, acetylene and aromatic olefins) trapped within the tunnel clathrate system of tris((9-phenylenedioxy)cyclotriphosphazene, induced by Co-y-radiation. The host was used in order to find if the concatenation and orientation of the monomer molecules under the steric forces generated within the host crystal lattice will lead to stereospecific polymerization. The clathrate was prepared by addition of liquid butadiene to the pure host at low temperature. The irradiation was conducted at low temperatures. Irradiation of pure butadiene (unclathrated bulk monomer) leads to formation of a mixture of three addition products f,2-adduct, cis- and trons-f,4-adducts. In contrast, the radiation-induced polymerization within the tunnel system of the host yielded almost pure trans-1,4-polybutadiene. A small percentage of f, 2-addition product was observed, but no evidence for the formation of c/s-f,4-adduct was found, confirming the earlier observation by Fin ter and Wegner. The average molecular weight was about 5000,... 

Humulene (1) is readily purified as the silver nitrate adduct, Ci,Ha,-2 AgNO,. It is regenerated by steam distillation or by treatment with aqueous ummuniu. Dthjdrobromtnallon. Silver nitrate in ethanol proved to be u very clibclivc agent... 

Thus, the Pyrex-filtered irradiation of an acetonitrile solution of 2,3-diazabicy-clo[2.2.1]hept-2-ene 1 (R, R, R, R = H) in a Rayonet photoreactor in the presence of nitr-oxide and with benzophenone employed as a triplet photosensitizer gave bicyclo[2.1. Ojpentane (4) in 40% yield and the two bis-nitroxide adducts cis- and trans-5 in 21 and 39% yields, respectively, based on 60% conversion. Separately generated bicyclo[2.1.Ojpentane was shown to be unreactive towards the nitroxide under the conditions of the photolysis furthermore no reaction occurred in the absence of light. However, these bis-nitroxide photoadducts were also produced, albeit to a smaller extent, when the reaction was carried out in the absence of benzophenone, implying that the nitroxide itself may act as a sensitizer. This triplet cyclopenta-1,3-diyl diradical has also been generated in the gas phase. ... 

In addition to the examples with alkene substitution, photocycloadditions of enones containing optically active ester substituents were investigated. Irradiation of a toluene solution of cy-clopentene and the chiral enone esters 13a-c gave two types of diastereomeric adducts, cis-anti-cis 14a-c and cis-syn-cis 15a-c77. By varying the size of the chiral auxiliary R the cyclobutane ring junctions syn- vs. anri-adducts) as well as the degree of asymmetric induction is altered. It is possible to obtain high enantiomeric excesses (e.g., 79% for 15a). 

Photoaddition of dimethyl acetylenedicarboxylate to 1-methylindole affords the cyclobuteno-indole (221) the same type of adduct is formed from 1,3-dimethylindole. The latter reaction yields six other products, which include the Michael adducts cis- and trans- 222) and the 1 2 adducts cis- and trans-(223). There is evidence from i.r., n.m.r., and mass spectroscopy that... 

As described in Chapters 2 and 3, the monomer can be inserted into the polyisoprene chain potentially in nine different ways. These are the three tactic forms of the 1,2-adducts, two 1,4-adducts, cis and transy and three tactic forms of 3,4-adducts. In addition, there is some possibility of head-to-head and tail-to-tail insertion, though the common addition is head-to-tail. Table 5.8 presents the various microstructuies that can be obtained in polymerizations of isoprene with different catalysts. 

SCHEME 2.10 Kinetic scheme for the formation of adducts cis- and trans-11, computed at M06(MS8)//B3LYP(PCM). Numbers on the arrows are the corresponding Gibbs activation energies (in kcal/mol). Numbers in parenthesis are relative Gibbs energies (in kcal/mol) with respect to 19. 

FIGURE 6.4 The structures of 2-aIkenal adducts, (a) The structures of acrolein adducts (1 3). (b) The structures of 2-nonenal adducts (cis- and frans-HHP-lysine) (4 and 5). 

As mentioned above, organolead hydrides are also capable of undergoing polar reactions. That this is true can be observed in the hydroplumbation of alkynes 195), where during the addition of MejPbH to cyanoacetylene in diethyl ether the /3-adducts (cis and trans) are formed almost exclusively, whereas 76% of a-adduct is formed in butyronitrile as solvent, probably by means of an ionic reaction (Table XII.)... 

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