Tert hypohalite

Ghlorohydrination with er -All l Hypohalites. Olefins react with ethyl hypochlorite [624-85-1] to form the corresponding chlorohydrin (49). In 1938 both Shell Development Co. (50) and Arthur D. Litde, Inc. (51) patented the preparation of chlorohydrins by the reactions of olefins with tertiary alkyl hypochlorites. Examples with ethylene and propylene in the Shell patent reported chlorohydrin yields of greater than 95% with tert-huty hypochlorite [507-40-4]. 

The most widely used, and often most convenient reagents for such one-pot reactions are sodium hypochlorite (45) or hypobromite (16). These reactions are performed in the presence of an organic base (generally triethylamine) that normally enhances the yield of cycloaddition products (45). This method was employed for many intermolecular reactions (71) and also seems especially suited for intramolecular ones (72-77) as well as for the solid-phase synthesis (78) of 2-isoxazolines. Hypohalite can also be replaced by sodium broruite in combination with a catalytic amount of tri-u-butyltin chloride (79). In a related method, O-tributylstannyl oximes were treated with tert-butyl hypochlorite to produce nitrile oxides that were trapped with aUcenes or alkynes to afford the corresponding isoxazolines or isoxazoles in moderate to good yield (80). 

Boron trifluoride and boron trifluoride-diethyl ether complex can be used as a source of fluoride ions in the presence of hypobromites and hypochlorites, e.g. methyl hypobromitc, tert-butyl hypobromite, methyl hypochlorite in carbon tetrachloride at 25 C. The addition of bromine monofluoride" and chlorine monofluoride" to various alkenes is accompanied by the formation of the corresponding alkoxybromides and alkoxychlorides which hinder the isolation of the halofluorinated products.57 jV-Bromo- and A -chloro-substiluted alkyl- and arylamines. -amides, and -imides, A -chloro-A,-methylamine, A -bromo-A -methylamine, A -chloro-A, /V-dimethylamine, A-bromo-A.A-dimethylamine, ACV-dichloro-A -methylamine, V,fV-dibromo-,V-mcthylaminc, A -bromosuccinimide, -V-chlorosuccinimide, Af-bromoacct-amide, A.A -dichlorourethane, can be used in the reaction instead of the hypohalites. The reactions with various alkenes conducted in dichloromethane at room temperature in the presence of boron trifluoride-diethyl ether complex produce bromofluoro and chlorofluoro addition products in 40-80 % yield. However, the reactions are complicated by the addition of A -halo-succinimides and Af.A-dichlorourcthane to the C = C bonds.58... 

Other alkyl hypohalites usually add to carbon-carbon multiple bonds in a free-radical process.155-158 Ionic additions may be promoted by oxygen, BF3, or B(OMe)3.156-160 While the BF3-catalyzed reaction of alkyl hypochlorites and hypo-bromites gives mainly halofluorides,159 haloethers are formed in good yields but nonstereoselectively under other ionic conditions.156-158 160 In contrast, tert-BuOI reacts with alkenes in the presence of a catalytic amount of BF3 to produce 2-iodoethers.161 Since the addition is stereoselective, this suggests the participation of a symmetric iodonium ion intermediate without the involvement of carbocationic intermediates. 

Haloform reactions are generally performed with halogens in the presence of hydroxide [251] or directly with hypohalites [252]. Alternative methods affording carboxylic acids from methyl ketones (or other enolizable substrates) include the aerobic oxidation in the presence of a catalytic amount of dinitrobenzene [253] with a base in a dipolar aprotic solvent such as DMF [254] or HMPT (hexamethylphospho-ric triamide) [255, 256] and the use of stoichiometric quantities of hypervalent iodide derivatives [95, 257] or nitrosylpentacyanoferrate [258]. Furthermore, metal catalysts can be used, and systems such as tert-butyl hydroperoxide in the presence of rhenium oxide [259], oxygen in combination with a copper complex [260], heteropolyacids [261] and Mn"/Co" systems [262] were found to be applicable. Finally, aryl ketones are selectively oxidized to aliphatic carboxylic acids by treatment with periodate [81] in the presence of ruthenium trichloride [263]. 

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