Reactions adduct formation

In each case the configuration around the boron changes from trigonal planar to tetrahedral on adduct formation. Because of this ability to form additional compounds, boron trifluoride is an important catalyst and is used in many organic reactions, notably polymerisation, esterification, and Friedel-Crafts acylation and alkylations. 

Hartshorn and Thompson have also found evidence for adduct formation with o-xylene, n.m.r. investigations of the reaction solution revealing peaks in... 

The reaction was studied in the absence, and presence, of (MeO)2AlMe as a model catalyst for the BINOL-AlMe system. The change in relative energy for the concerted hetero-Diels-Alder reaction, and formation of the hetero-Diels-Alder adduct 11 via a Mukaiyama aldol reaction, is shown in Fig. 8.13. The conclusion of the study was that in the absence of a catalyst the concerted reaction is the most... 

There is significant metal-metal bonding in the platinum compound, whose geometry involves a square of platinum atoms another important difference is that the coordination geometry is square planar in palladium acetate but octahedral in the platinum analogue. Different oligomers exist in solution, broken down by adduct formation. Palladium(II) acetate may be obtained as brown crystals from the following reaction [65] ... 

The dominant state in the adduct formation is clearly the adduct. Further, the shifts for the uncomplexed ketone are best fitted by the ajj(BA)> whereas those for the adduct state are best fitted by, in accord with structural expectations. Because the adduct state is dominant in the complex formation equilibrium, the A values are also best fitted by the Or scale. The values for the individual states (summarized in Table XVIII) for this reaction (as well as other similar examples for BF3, BBr3 and adducts) are consistent with the idea that increasing pi electron demand at the reaction center increases the -Pr... 

As is the case with the Wittig and Peterson olefinations, there is more than one point at which the stereoselectivity of the reaction can be determined, depending on the details of the mechanism. Adduct formation can be product determining or reversible. Furthermore, in the reductive mechanism, there is the potential for stereorandomization if radical intermediates are involved. As a result, there is a degree of variability in the stereoselectivity. Fortunately, the modified version using tetrazolyl sulfones usually gives a predominance of the E-isomer. 

Bolton, J. L. Le Blanc, J. C. Y. Siu, K. W. M. Reaction of quinone methides with proteins analysis of myoglobin adduct formation by electrospray mass spectrometry. Biol. Mass... 

In the second campaign in our pilot plant, however, there was a surprise. Adduct formation was completed with less than 0.1% starting material 32 remaining as expected, but after thermolysis the chemical engineers came to us with a problem. An assay of the reaction showed about 1% (and not 0.1% as we expected) of 32 Considering that 32 would not be rejected in isolation of the product, this was a big problem. 

The dehydrogenation reaction was generally monitored by taking samples for reversed phase H PLC analysis. Diode array detectors for H PLC were relatively new at that time and proved valuable for quickly getting structural information on products of the reaction produced under different conditions. Key reaction parameters for adduct formation, overall concentration, BSTFA, TfOH, and DDQ charges, were optimized using a thermostated HPLC autosampler to sample reactions directly for analysis. Comparison of reaction profiles provided rate and reaction time information that was used to select a more limited number of reaction conditions that were scaled up to compare yields. 

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