Naphthyl acetylene

Using tryptamine as the nucleophile, the Michael addition-cyclization strategy was extended to the enantioselective synthesis of the /J-carboline alkaloid system. Michael addition of tryptamine to the chiral acetylenic sulfoxides took place smoothly at room temperature. Either trifluoroacetic acid or p-toluene-sulfonic acid was effective as a catalyst for the cyclization step (Scheme 7). The results of the Michael addition-cyclization reaction sequence are summarized in Table 3. In general, we found that the indole moiety is more reactive than the dimethoxyaryl ring used in the tetrahydroisoquinoline synthesis. Therefore, the cyclization step could take place at a temperature as low as -60 °C. Also, p-tolu-enesulfonic acid resulted in a better diastereoselectivity. However, the diastereo-selectivity of the system is much less sensitive to the aryl substituents of the acetylenic sulfoxides compared to that of the tetrahydroisoquinoline system. Also, to our surprise, the steric factor on the chiral acetylenic sulfoxide has little effect on the diastereoselectivity. Even with the bulky 2-methoxy-naphthyl acetylenic sulfoxide lc [11], the diastereoselectivity still remained roughly the same as for 1 a and 1 b (Scheme 7) (Table 3). 

The potential energy surfaces of the two processes are shown in Figure 6.23. As can be seen, the surfaces are very similar. Both radicals react via two parallel channels. In one channel (via TSl), both eject an H-atom to produce naphthyl ethylene and naphthyl acetylene with energy barriers of 35 and 38 kcaFmol, respectively. In the second channel (via TS2) with energy barriers of 17.3 and 19.3kcaFmol, they isomerize to acenaphthalenyl (INTeth) in surface (II) and acenaphthylenyl (INTac) in surface (I) toward the formation of acenaphthene and acenaphthylene. Since the... 

The question that arises is why naphthyl ethylene is formed in the reaction of naphthyl radicals with ethylene, whereas naphthyl acetylene is not formed at aU in the reaction with acetylene, although the barriers from 1-naphthyl ethylenyl and 1 -naphthyl acetylenyl for their production are very close ( 17 and 19 kcal/mol in the first step, and 30 (9.8 - - 19.7) and 28 (18.8 + 9.1) kcal/mol in the second step) (Figure 6.23). 

Ohtori, T. Masuda, T. Higashimura, T. Polymerization of phenylacetylenes. IX. Polymerization of fi-naphthyl-acetylene by WClg and M0CI5. Polym. J. 1979, 77, 805-811. 

In addition to inorganic radicals, which profoundly modify the properties of a paraflSn hydrocarbon residue, there is a whole series of organic groupings which are distinguished by exceptional reactivity, for example, the ethylene and acetylene groupings, and the phenyl and naphthyl radicals. Thus the characterisation of unsaturated hydrocarbons and their derivatives, e.g., the aromatic compounds, becomes possible. 

Under the conditions favorable for the synthesis of pyrroles from alkyl aryl ketoximes (100°C, 3 hr, 30% KOH of ketoximes mass, DMSO, acetylene under 12-16 atm pressure), the reaction with methyl naphthyl ketoximes is accompanied by considerable resinification to give low yields of pyrroles 14-17. The best results were achieved at 90°C. From methyl 1-naphthyl ketoxime at this temperature (2 hr, KOH), 2-(l-naphthyl)pyrrole (14) and 2-(l-naphthyl)-1-vinylpyrrole (15) are formed in 15 and 48% yield, respectively. 

In general, however, methyl 1-naphthyl ketoxime starts to condense with acetylene under pressure at about 60°C. At 80°C (3 hr, KOH) 2-(l-naphthyl)- 1-vinylpyrrole (15) becomes the predominant reaction product, however its yield decreases due to resinification on further elevating the temperature and increasing the reaction time. 2-(l-Naphthyl)pyrrole (14), free from the corresponding N-vinylpyrrole (15), was isolated in 22% yield when use was made of a catalytic pair LiOH/DMSO (90°C, 3 hr). The temperature effect (3 hr, 30% KOH, initial acetylenic pressure of 12 atm) on the yield of naphthylpyrroles was examined in condensation of methyl 2-naphthyl ketoxime with acetylene as an example (82KGS1351) ... 

Apart from copper(I)-mediated reactions, few studies of the treatment of vinyliodonium salts with carbanions have appeared. The vinylations of the 2-phenyl- and 2- -hexyl-l,3-indandionate ions shown in equations 222 and 223 are the only reported examples of vinyliodonium-enolate reactions known to this author26,126. ( ,)-l-Dichloroiodo-2-chloroethene has been employed with aryl- and heteroarvllithium reagents for the synthesis of symmetrical diaryliodonium salts (equation 224)149,150. These transformations are thought to occur via the sequential displacement of both chloride ions with ArLi to give diaryl (/ -chlorovinyl)iodanes which then decompose with loss of acetylene (equation 225). That aryl(/ -chlorovinyl)iodonium chlorides are viable intermediates in such reactions has been shown by the conversion of ( )-(/ chlorovinyl)phenyliodonium chloride to diaryliodonium salts with 2-naphthyl- and 2-thienyllithium (equation 226)149,150. 

Deamination of a-substituted- 3-2-(5-nitrofuryl)vinylamines 43 (R = substituted Ph, 1-naphthyl, 2-furyl) with isoamyl nitrite in dioxane at 80 °C gives p-2-(5-nitro-furyl)acetylenes 44 in good yields . 

Intermolecular oxidative addition of H—C usually involves activated H—C bonds. The weak acid HCN reacts with transition-metal complexes e.g., HCN and NiL lead to the hydride complexes HNi(CN)Lj (L = various phosphorus ligands). The versatile complex IrCl(CO)(PPh3)j adds HCN cleanly in CH Clj at RT to form HIr(CN)(Cl(PPhj)2. The zero-valent complexes Pt(PPhj) or Pt(PPh3)3 also add HCN to yield HPt(CN)(PPh3)j. Reactions of HMNp(dmpe)j (M = Fe, Ru, Os Np = 2-naphthyl dmpe = Me PCH CH PMej) with HCN and terminal acetylenes give HMR(dmpe)2 that contain new M—C bonds (R = — CN, — CjR ) . 

Ester-based chiral auxiliaries have also beat used in other settings. P-Alk-oxyesters 1.27 of (R)-1 -phenylethanol 1.1 (R = Me, Ar = Ph) or (5)-1-naphthyl-ethanol 1.1 (R = Me, Ar = 1-Np) are transformed into dural synthons by reactions with a lithiated carbanion a to phosphorous followed by hydrogenolysis [194], Ethers 1.28 of chiral alcohols 1.1 undergo selective alkylations or hydroxyalkyla-tions [169]. The auxiliaries can be removed by hydrogenolysis. Enol or dienol ethers 1.29 and 1 JO suffer [2+2] [195, 196] or [4+2] cycloadditions [49, 197,198, 199], The best stereoselectivities are obtained when the chiral auxiliary is 1.1 (R = r-Pr, Ar=Ph), 1.4 (R=Ph), 1.5 (R = Ph), 1.10 or 1.13. These auxiliaries are cleaved either by acid treatment [199] or by other means in subsequent steps. Acetylene ethers G OC=CR derived from 1.5 (R=Ph) [199a] can undergo stereoselective Pauson-Khand reactions [200, 201], The auxiliaries are removed by treatment of the products with Sml2 in THF-MeOH. 

In this section, studies on the reactions of naphthyl radicals with unsaturated aliphatic hydrocarbons toward the production of three fused rings and of aliphatic residues attached to naphthalene are described. This is an effort to examine the process of polycyclic aromatic hydrocarbon (PAH) growth [88-99]. The source of naphthyl radicals for the experimental study was naphthyl iodide, in view of its low C—I bond dissociation energy. It dissociates very fast following the reflected shock heating. The unsaturated aliphatic hydrocarbons that have been studied were ethylene [28] and acetylene [29]. 

The reactions between naphthyl radical and both ethylene and acetylene are attachment reactions. The reaction with ethylene produces naphthyl ethylenyl radical and with acetylene the product is naphthyl acetylenyl, both with almost no barrier [28,29,88,96]. The attachment products are shown in Figure 6.22. 

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