Fragmentative elimination

Herein is described a much simpler dehydrohalogenation alternative that had been earlier applied successfully to the preparation of ketene acetals6-7 and 2-alkylidene-1,3-dithianes.8 This route appears not to have been examined for preparing the title compound because of an early report that 2-lithio-1,3-dithiolanes undergo ready fragmentative elimination to form ethylene and dithlocarbonate unlike... 

The ions of the C series are formed from amino sugars by elimination of methanol (instead of the CH30- radical in the case of neutral hexosides). Subsequently, the fragment eliminates ketene and, at last, the CH3OCH2-radical. This sequence is not observed with the neutral hexosides, indicating the greater stability of the ammonium compared with the oxonium ion. 

Two further methods of fragment elimination seem to be generally applicable controlled pyrolysis and hard base induced disproportionation. The thermal Fe(CO)2 fragment removal from 15a which completes the reversible interconversion of 84 and 15a (61) has already been mentioned. Similarly the leaving group HRe(CO)s can be eliminated thermally from 92 yielding the stable unsaturated cluster H3Re3(CO) o 13 (175). 

Although the elimination of C2H6 is the lowest energy process for 3-pentanone, Et is the main fragment eliminated in the source, in the CAD352 and in the charge-transfer... 

Other neutral fragments eliminated in the fragmentation processes of tris-(dimethylamino) phosphine metal carbonyl complexes appear to contain phosphorus-hydrogen bonds, e. g. 

No evidence is available which indicates whether the neutral fragment eliminated in (1) is cyanic, isocyanic, or even fulminic acid or whether the neutral fragment eliminated in (3) is phenyl isocyanide or benzonitrile. These features of the mass spectrum of... 

Lange, G. L., Gottardo, C., Merica, A. Synthesis of Terpenoids Using a Free Radical Fragmentation/Elimination Sequence. J. Org. Chem. 1999, 64, 6738-6744. 

Eliminations Involving Sulfur and Selenium Fragmentation Elimination of Sulfides and Selenides... 

Monovalent polyclonal Fab fragments of enzyme coupled secondary immunoglobulins have also been used to reduce or eliminate cross-reactions when using more than one primary antibody from the same species. The polyclonal nature of the secondary allows it to saturate all possible epitopes on the first primary antibody, while the monovalent property of the Fab fragment eliminates the possibility that an unsaturated arm on a divalent secondary may bind subsequent primary antibodies of the same species during their application (35). 

Fragmentative elimination. Cyclobutoxime benzoates are converted to unsaturated nitriles (except for the 3,3-disubstituted members whose products cannot accommodate a double bond). ... 

A few of the synthetic methods adopted so far are closely related to the previously examined methods used for the synthesis of clusters containing interstitial or exposed main group elements or elemental organic fragments. For example, as shown in Scheme 3-11, the very peculiar [Bi4Fe4(CO),3] cluster (see Section 3.2.6) has been obtained in two steps through classical redox condensation reactions or by the clockwise condensation induced by fragment elimination. [312] Related syntheses have also been used for the E-Co (E = Sb,Bi) [314, 315] and n-Fe [309] mixed clusters listed in Ihble 3-11. 

In the case of cyclopentane, the most abundant fragment results from the simultaneous cleavage of two bonds. This mode of fragmentation eliminates a neutral molecule of ethene (MW = 28) and results in the formation of a cation at m/e = 42. 

These results suggest a fragmentation-elimination route by way of a 3 -hydroxy or 3 -acyloxymarmesin (29) or, in the angular case, a similar 3 -substituted columbianetin ( 3). ... 

Fig. 6. Possible fragmentation-elimination mechanism of cis or trans-3 -hydroxymarmesin leading to furanocoumarins.

A variant of the Eschenmoser fragmentation eliminates the need for prior preparation of the epoxy-ketone " [e.g. (232) - (233)]. 

Fragmentation Elimination of water from M" ", followed by loss of alkyl or alkenyl residues. Ring cleavage at the O-bearing C atom, followed by loss of alkyl residues after H rearrangement. 

Fragmentation Elimination of HCN (Am 27) followed by loss of an alkyl group. The cleavage of the C-C bond next to SCN is unimportant except in short-chain thiocyanates. 

A possible process for the SiOx film deposition at low temperatures below 70°C may be a special plasma CVD method which involves some elimination of carbonaceous compounds. In the plasma CVD, we believe that SiOx films are formed in two reactions (1) the bond scission of Si-OC bond in TEOS to form Si or SiO radicals, and (2) the recombination between two radicals to form Si-O-Si linkage. The repetitious combination of the two reactions leads to the Si-O-Si network, and as a result, a SiOx film is deposited. On the other hand, fragments eliminated from TEOS, ethyl or ethoxy radicals, also are recombined to form carbonaceous compounds and incorporated into the SiOx film. In the conventional plasma CVD process, the carbonaceous compounds in the deposited SiOx film are eliminated by the pyrolysis of the SiOx film at high temperature (500 ) (2). Therefore, in the SiOx-deposition on the PET film surface, some special process for the elimination of the carbonaceous compounds instead of the pyrolysis treatment should be investigated. 

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