Ethers Halogens

With respect to the carbonyl substrate, a variety of additional functional groups is tolerated, e.g. ester, ether, halogen. With compounds that contain an ester as well as a keto or aldehyde function, the latter usually reacts preferentially. Due to its mild reaction conditions the Wittig reaction is an important method for the synthesis of sensitive alkenes, as for example highly unsaturated compounds like the carotinoid 17 shown above. 

Early transition states in enol ether halogenation 263... 

EARLY TRANSITION STATES IN ENOL ETHER HALOGENATION... 

Imbalance between polar and resonance effects in enol ether halogenation... 

Note that the ether, halogen, and —N02 groups are always denoted by prefixes in systematic nomenclature. 

The mildness of these reagents tolerates the presence of various functional groups such as ester, ether, halogen, and nitrile. The stereospecific cis nature of hydroboration gives exclusively the tram alkenylboranes, often also in high regioisomeric purity (Eq. 53). On the other hand, highly pure (Z)-l-alkenyl-dialkylboranes are prepared without any difficulty via the monohydroboration of 1-halo-1-alkynes with disiamyl-borane or dicyclohexylborane, followed by treatment with t-butyllithium (Eq. 55)106). 

Solubility. —White phosphorus is almost insoluble in water. It dissolves easily in liquid ammonia, sulphur dioxide and cyanogen, also in such compounds as phosphorus trichloride which mix with typical organic solvents. It is moderately soluble in fatty oils, also in hydrocarbons, alcohols, ethers, halogenated hydrocarbons such as chloroform and especially methylene iodide. One of the best solvents for phosphorus, as for sulphur, is carbon disulphide, which seems to dissolve it in all proportions at ordinary temperatures a solution has even... 

The synthetic interest of the reaction is even broader since several functional groups in the substrate, such as C=C double bond, ether, halogen, ester, and amide groups (entries 6-10) can be present in the carbon skeleton. Chemose-lective cyclopropanation reactions involved the enone functionality in the presence of a saturated ketone group (Scheme 9). Recently, the reaction was applied to the conversion of 1,3-dicarbonyl compounds into 2-alkoxyalkenyl cyclopropanes (Scheme 10) [15]. These molecules having both vinylcyclopropane and enol ether moieties are supposed to be versatile synthetic intermediates. 

Oxidizer, Poison, Corrosive SAFETY PROFILE Poisonous and corrosive. Very reactive, a powerful oxidizer. Explosive or violent reaction with organic materials, water, acetone, ammonium halides, antimony, antimony trichloride oxide, arsenic, benzene, boron, bromine, carbon, carbon monoxide, carbon tetrachloride, carbon tetraiodide, chloromethane, cobalt, ether, halogens, iodine, powdered molybdenum, niobium, 2-pentanone, phosphoms, potassium hexachloroplatinate, pyridine, silicon, silicone grease, sulfur, tantalum, tin dichloride, titanium, toluene, vanadium, uranium, uranium hexafluoride. 

A Aliphatic ethers Halogenated ethers o Aromatic ethers... 

Applicability Particularly accurate for the following families acetates, aliphatic ethers, halogenated compounds, dicarboxylic acids, ketones, aliphatic alcohols, aliphatic acids, propionates and butyrates, and unsaturated aliphatic esters. 

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