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The designations 1,2 and 1,4 are derived from numbering the atoms of the starting compound where the oxygen is labeled “1” and each atom adjacent to the oxygen are sequentially numbered out to the site of nucleophilic addition. A 1,2-addition occurs with nucleophilic addition to position 2 while a 1,4-addition occurs with nucleophilic ...
This reaction produced the 1,6-addition product 2 in 0% yield, the 1,6-addition product 3 in approximately 99% yield, and the 1,4-addition product 4 in less than 2% yield. This particular catalyst and set of reaction conditions led to the mostly regioselective and enantioselective 1,6-Michael addition of ethyl sorbate 1 to product 3 .
In one study, seven-membered rings were constructed in a tandem 5-exo-dig addition reaction / Claisen rearrangement: [6] A 6-endo-dig pattern was observed in an allene - alkyne 1,2-addition / Nazarov cyclization tandem catalysed by a gold compound: [7] A 5-endo-dig ring closing reaction was part of a synthesis of (+)-Preussin: [8]
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In this notation, a Diels-Alder reaction is a (4+2)cycloaddition and a 1,3-dipolar addition such as the first step in ozonolysis is a (3+2)cycloaddition. The IUPAC preferred notation however, with [i+j+...] takes electrons into account and not atoms. In this notation, the DA reaction and the dipolar reaction both become a [4+2]cycloaddition.
Lithium dimethylcopper (CH 3) 2 CuLi can be prepared by adding copper(I) iodide to methyllithium in tetrahydrofuran at −78 °C. In the reaction depicted below, [4] the Gilman reagent is a methylating reagent reacting with an alkyne in a conjugate addition, and the ester group forms a cyclic enone. Scheme 1. Example Gilman reagent reaction
Thermolysis converts 1 to (E,E) geometric isomer 2, but 3 to (E,Z) isomer 4.. The Woodward–Hoffmann rules (or the pericyclic selection rules) [1] are a set of rules devised by Robert Burns Woodward and Roald Hoffmann to rationalize or predict certain aspects of the stereochemistry and activation energy of pericyclic reactions, an important class of reactions in organic chemistry.
A recent example of the Fürst-Plattner rule can be seen from Chrisman et al. where limonene is epoxidized to give a 1:1 mixture of diastereomers. Exposure to a nitrogen nucleophile in water at reflux provides only one ring opened product in 75-85% ee. [4]