Triple bonded systems

The addition of nucleophiles to double and triple bond systems is often a convenient way of effecting an intramolecular ring closure. Addition to cyano groups has received considerable attention, as in addition to ring formation it provides a convenient method for the introduction of an amino group. Reaction of methyl Af-cyanodithiocarbimidate with Af-methylaminoacetonitrile resulted in displacement of methanethiol and formation of (314). Sodium ethoxide treatment in DMF converted (314) into a 4-amino-5-cyanoimidazole... 

In acetylene or triple-bonded systems, there will be a second pair of ( cc> xcc) orbitals with axes parallel to the y direction. 

Therefore, it appears that the overall agreement obtained for a variety of spectroseopie eonstants is comparable for the two methods while the present method allows us to use a more compact wavefunction. It should also be noted that a good Cl description of a triple bonded system involving a third period atom is much harder to achieve. It can be concluded that the shape of the theoretical potential energy curve reflects its experimental counterpart with acceptable accuracy in the interatomic region of interest. 

K. Tani and Y. Kataoka, begin their discussion with an overview about the synthesis and isolation of such species. Many of them contain Ru, Os, Rh, Ir, Pd, or Pt and complexes with these metals appear also to be the most active catalysts. Their stoichiometric reactions, as well as the progress made in catalytic hydrations, hydroal-coxylations, and hydrocarboxylations of triple bond systems, i.e. nitriles and alkynes, is reviewed. However, as in catalytic hydroaminations the holy grail", the addition of O-H bonds across non-activated C=C double bonds under mild conditions has not been achieved yet. 

Reaction with Activated Triple-Bond Systems... 

Scheme 25. Reaction of 1 with CN triple-bond systems.

The [3+2] cycloaddition of azides to double and triple bond systems has found considerable interest over the last couple of years. The reaction can either be performed under thermal conditions or by copper(i) catalysis <2001AG(E)2004, 2002AG(E)2596>. In an attempt to broaden the chemistry of such cycloaddition processes, Sharpless et al. reported the generation of tetrazole derivatives 61 by an intramolecular process (Scheme 12). In... 

These considerations led us to the conclusion that suitable triple-bond systems A=B (or compounds containing cumulative double-bond systems A=B=C) might be found that add pyranoses and furanoses under base... 

The most reliable information on the structure of the polymer has been derived from X-ray diffraction and Raman-spectroscopic studies. In a few cases it has been possible to determine in detail the structures of both the monomer and the corresponding polymer. From such measurements and other optical studies the process is considered to be 132 — 133 for a symmetric diacetylene. In polymerizable structures the diacetylene rods are inclined at about 45° to the translation (stack) axis, with the ends of each diacetylene moiety approaching the adjacent triple-bond systems to a distance of s4 A. The polymer is a planar system in extended conformation and having alternate R groups trans to one another. 

The bonding situations of the products presented in this section are discussed below as bridging phosphido triple-bond systems. 

Substituted cyclopropyl rings conjugated with a triple bond system have recently received attention as C5 building blocks. The procedure described here is a modification of the decarboxylation-elimination reaction for the preparation of a.3 acetylenic acids from enol sulfonates of acyl malonates. Addition of aqueous alkali to the enol sulfonate of diethyl cyclopropyl carbonyl malonate gives cycl opropyl propiol ic acid, but the yield is 1 ow. 

Cycloadditions with Triple-Bond Systems KSeCN... 

Both Grignard and R CuLi reagents523 have also been added to triple-bond systems of the form Ge=C—C=0.524... 

Tt-methane rearrangement,601 generally occurs only from the triplet state), to 3,y-unsaturated imines,602 and to triple-bond systems.603... 

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