Ketones, addition derivatives chlorination

The methoxide ion uses of its lone pairs of electrons to form a bond to the electrophilic carbonyl carbon of the acid chloride. Simultaneously, the relatively weak n bond of the carbonyl group breaks and both of the n electrons move onto the carbonyl oxygen to give it a third lone pair of electrons and a negative charge. This is exactly the same first step involved in nucleophilic addition to aldehydes and ketones. However, with an aldehyde or a ketone, the tetrahedral structure is the final product. With carboxylic acid derivatives, the lone pair of electrons on oxygen return to reform the carbonyl n bond (Step 2). As this happens, the C-Cl o bond breaks with both electrons moving onto the chlorine to form a chloride ion that departs the molecule. 

Tomboulian et al. (2002) has reported that butylated hydroxytoluene (BHT) can impart a "burnt plastic" odor and is an additive in HDPE pipes. Quinone may be derived from BHT due to interactions with residual chlorine in pipes (Anselme et al., 1985). Yam et al. (1996) reported that antioxidants, such as vitamin E, Irganox 1010, and BHT, contributed to off-flavors in water. Vitamin E yielded less off-flavor, possibly due to lower aldehyde and ketone concentrations. Extrusion temperatures over 280 °C and exposure time for melt contributed to more oxidation of LDPE films and higher intensities of off-flavors in water in contact with LDPE with different antioxidants (Andersson et al., 2005). 

Dimethyl sulfoxide and chlorine form highly reactive intermediates which are of some limited use as oxidants for alcohols. These intermediates are related to those derived from the reaction of the halogens with dimethyl sulfide and probably have a structure such as (27). When formed at -4S C they allow the oxidation of primary and secondary alcdiols to aldehydes and ketones when used in a two-fold excess. For very simple alcdiols the reaction proceeds in yields of greater than 90%, but there are considerable drawbacks if some types of additional functionality are present in the molecule, e.g. alkenes react very rapidly to form vicinal dichlorides. 

A convenient way selectively to introduce a chlorine atom into the methyl group of a methyl ketone has been developed. It involves treatment of the imine, formed from the reaction of the methyl-keto-group with ethanolamine, with Af-chlorosuccinimide (see Part II, Chapter 1, ref. 311 and also refs. 149-151 and 156). Various 3-trifluoromethyl derivatives have been prepared by photolytic addition of trifluoroiodomethane across the A -double-bond. ... 

On the other hand, reaction of 8,8-dichlorobicyclo[4.2.0]octan-7-one with sodium methox-ide gave a 20 1 mixture of exo- and cnt/o-methyl l-methoxybicyclo[4.1,0]heptane-7-carboxylate (16) in 70% isolated yield. Addition of methoxide to the enolized a,a-dichloro ketone and elimination of one chlorine gave, most probably, the 8-chloro-l-methoxybicyclo[4.2.0]octan-7-one by cine substitution this intermediate then underwent ring contraction by action of a second methoxide anion to give the norcarane derivatives. ... 

ACSA(B)62]. The stannanes are available from enol ethers by a-lithiation and quenching with trialkylstannyl chloride. The coupling reactions have been run on derivatives that had either a chlorine atom in an activated position or a bromine atom in the benzenoid position. Mild acid hydrolysis of the a-pyrimidinylalkenyl ethers yields ketones, the acyl-substituted pyrimidines. In the 4,5-dichloro derivative (130), the masked acyl group is introduced into the electrophilic 4-position (131). In the 2,5-disubstituted pyrimidine (133), having a methyl group in the 5-position and a chlorine atom in the 2-position results in the addition of a masked acyl group in the electrophilic 2-position (134). When the 5-substituent in the latter example is a bromine atom, the chemoselectivity leads to masked acylation in 5-position (135). This reaction sequence constitutes a convenient... 

One representative synthesis of prothioconazole starts [95] with the addition of the Grignard derivative of 2-chlorobenzyl chloride on the carbonyl double bond of chloromethyl 1-chloro-cyclopropyl ketone (Scheme 17.19). The untouched chlorine atom of the chloromethyl group is then classically substituted with 1,2,4-triazole. From this intermediate, one way to obtain the 2,4-dihydro-3H-l,2,4-triazole-3-thione of prothioconazole is by direct lithiation of the 1,2,4-triazole at position 5 with n-butyl lithium and reaction with sulfur. The commercially available compound is a mixture of two enantiomers (chirality of the quaternary carbon bearing the hydroxy group). 

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