1.1- Dihalides aldehydes

Perfluoroalkyltin halides can be prepared via oxidative addition of perfluo-roalkyl iodides to tin(II) halides in dimethylformamide (DMF) [12] The per-fluoroalkyltin(IV) dihalide could not be isolated, but in DMF solution, the tin(lV) compound did react with aldehydes and ketones in the presence of pyndine [12] (equation 8) Typical perfluoroalkylcarbinols prepared by this method are shown in Table 1 [12]... 

Instead of formaldehyde, other aldehydes or ketones may be used—aliphatic as well as aromatic recently methylene dihalides have been employed with success. The amine component is often employed as hydrochloride in addition to... 

The chemistry of alkynes is dominated by electrophilic addition reactions, similar to those of alkenes. Alkynes react with HBr and HC1 to yield vinylic halides and with Br2 and Cl2 to yield 1,2-dihalides (vicinal dihalides). Alkynes can be hydrated by reaction with aqueous sulfuric acid in the presence of mercury(ll) catalyst. The reaction leads to an intermediate enol that immediately isomerizes to yield a ketone tautomer. Since the addition reaction occurs with Markovnikov regiochemistry, a methyl ketone is produced from a terminal alkyne. Alternatively, hydroboration/oxidation of a terminal alkyne yields an aldehyde. 

For a list of reagents that convert aldehydes and ketones to ge/n-dihalides or vinylic halides, with references, see Ref. 58, p. 372. 

Primary, secondary, and tertiary aliphatic amines have been cleaved to give aldehydes, ketones, or carboxylic acids with aqueous bromine and with neutral permanganate. The other product of this reaction is the amine with one less alkyl group. In a different type of procedure, primary alkyl primary amines can be converted to ge/n-dihalides, RCH2NH2 —> RCHX2 (X =Br or Cl), by treatment with an alkyl nitrite and the anhydrous copper(I) halide. 

The reaction of aldehydes with carbon tetrachloride in the presence of excess tris(dimethylamino)phosphine has been used to prepare vinyl dihalides in yields of 50—70%. It is suggested that the reaction takes place via an intermediate salt (77), although the formation of this salt seems more likely to be analogous to the Perkow reaction than to involve attack on oxygen. 

CHEC-II(1996) <1996CHEC-II(8)345> covered a range of reactions of substituents, including hydrolyses of esters to carboxylic acids and geminal dihalides to aldehydes, reduction of aldehydes and halogens directly attached to the ring, O-methylation with diazomethane, and reduction of nitroso compounds. A selection of reactions which have... 

This has been applied to the cyclization of dihalides [45, 46], nonconjugated, unsaturated ketones [47] and esters [48], oxoalkylpyridinium salts [49], aldehydes and unsaturated nitriles [50], halides, and unsaturated esters [51], The umpoled acceptors, mostly radical anions or carban-ions (see Scheme 1), can also be used in intermolecular reactions such as acylation, alkylation, or carboxylation (Eq. 5). 

Chromium(II) sulfate is a versatile reagent for the mild reduction of a variety of bonds. Thus aqueous dimethylformamide solutions of this reagent at room temperature couple benzylic halides, reduce aliphatic monohalides to alkanes, convert vicinal dihalides to olefins, convert geminal halides to carben-oids, reduce acetylenes to /raw5-olefins, and reduce a,j3-unsatu-rated esters, acids, and nitriles to the corresponding saturated derivatives. These conditions also reduce aldehydes to alcohols. The reduction of diethyl fumarate described in this preparation illustrates the mildness of the reaction conditions for the reduction of acetylenes and o ,j8-unsaturated esters, acids, and nitriles. 

The reducing properties of organic compounds of sulfur, such as methyl mercaptan, show up in partial reduction of trigeminal to geminal dihalides [243]. Dimethyl sulfide reduces hydroperoxides to alcohols and ozonides to aldehydes while being converted to dimethyl sulfoxide [244]. 

The Formation of gem-Dihalides from Aldehydes and Ketones Dihalo-de-oxo-bisubstitution... 

Oxidation of Amines or Nitro Compounds to Aldehydes. Ketones, or Dihalides Oxo-de-hydro.amino-bisubstitution (overall transformation)... 

The first step is a Takai reaction.4 Geminal dihalide 12 is presumably converted in the presence of ehromium(H) chloride into the di-chromium complex 13, which reacts with aldehyde 5 to give product 14. 

This method is well-suited to preparing tram double bonds from aldehydes and geminal dihalides. The Takai reaction leads to FJ7 se-lcctivities >90 10. often even 99 1 (for further details see Chapter 13). 

A simple method for introducing a triple bond into an organic compound is to treat an appropriate dihalide with a strong base. Since vicinal dihalides (usually the bromide) are readily formed by reaction of bromine with an alkene, and geminal dihalides from aldehydes or ketones with phosphorus pentachloride, the method is a useful general procedure for the preparation of terminal and non-terminal alkynes from readily available starting materials. 

Carbonylation of organolithium reagents in the presence of aldehydes and ketones or esters yields keto alcohols925 and diketones926, respectively. Lastly, phenyl lithium reacts with alkyl bromides and with 1,3-dihalides to give unexpected products (equations 166 and... 

Chlorofluoro compounds were electroreductivelv added to aldehydes to give the corresponding fluorinated alcohols (231) (equation 124)214. In this process platinum or lead are employed as the cathode, under constant-current conditions. The starting dihalides or trihalides (halogen = F, Cl or Br) can be prepared on an industrial scale by the reaction of the corresponding tri- or tetrahalide at a sacrificial anode (Zn, A1 or Mg)220. 

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