Hypohalites, acyl compounds

The first step is not a free-radical process, and its actual mechanism is not known. Compound 30 is an acyl hypohalite and is presumed to be an intermediate, though it has never been isolated from the reaction mixture. Among the evidence for the mechanism is that optical activity at R is lost (except when a neighboring bromine atom is present, see p. 899) if R is neopentyl, there is no rearrangement, which would certainly happen with a carbocation and the side products, notably RR, are consistent with a free-radical mechanism. There is evidence that the Simonini... 

A minor explosion in the use of gaseous acetyl hypofluorite was caused by inadvertent contact of the gas inlet tube with a cooling bath, which condensed liquid hypofluorite which subsequently exploded on contact with organic material or air [ 1 ]. More detail on the isolation of this compound of limited stability, particularly in the liquid phase, is given [2]. See other ACYL HYPOHALITES, OXIDANTS... 

Halogen cations afford hypohalogen acids or X2 + H20, or 7V-halo compounds. The HO- is obtained from water, which must be present in sufficient amount.261 The corresponding halohydrin ethers are formed when the reaction is carried out in an alcohol. Halogens and the silver salts of carboxylic acids in CC14 give acyl hypohalites RCOOX, which are added as X+ and RCOO- to C=C bonds at low temperatures.262-265... 

The route to 4-2 outlined here is unlikely to be profitable, because oxidation of Itydrazine leads to diimide, HNNH, rather than the dihydroxy hydrazine 4-4 [49], Precursor 4-3 is appeahng because it might be possible to photochemically extrade the very stable molecule benzene from it, providing 4. However, the bicyclic precursor to 4-5 suffers from the same kind of synthetic problem as 4-4. Indeed, organic compounds with N-O bonds are uncommon, and the synthesis of 4-2 or 4-3 may require some audacity. One unorthodox approach would be the reaction of a hydrazine metal salt ( rather inaccessible species [50]) with an acyl hypohalite [51], e.g. (surprisingly, 4-6 seems to be unknown) ... 

The latter is an extremely reactive species. The inductive effect of the trifluoroacetyl group makes it a good leaving group, and facilitates cleavage of the O-Br bond during reaction with an aromatic compound. The acyl hypohalites are also the active... 

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