Chloroform carbonyl compound/base reactions

Such copolymers of oxygen have been prepared from styrene, a-methylstyrene, indene, ketenes, butadiene, isoprene, l,l-diphen5iethylene, methyl methacrjiate, methyl acrylate, acrylonitrile, and vinyl chloride (44,66,109). 1,3-Dienes, such as butadiene, yield randomly distributed 1,2- and 1,4-copolymers. Oxygen pressure and olefin stmcture are important factors in these reactions for example, other products, eg, carbonyl compounds, epoxides, etc, can form at low oxygen pressures. Polymers possessing dialkyl peroxide moieties in the polymer backbone have also been prepared by base-catalyzed condensations of di(hydroxy-/ f2 -alkyl) peroxides with dibasic acid chlorides or bis(chloroformates) (110). 

REACTIONS OF THE CHLOROFORM/BASE SYSTEM WITH CARBONYL COMPOUNDS... 

A newcomer in the family of oxidants, introduced in 1983, Dess-Martin reagent is presently a well-established oxidant. Its main function is the extremely facile oxidation of primary and secondary alcohols to carbonyl compounds, at room temperature no further oxidation of aldehydes occurs. The reaction is conveniently carried out in dichloromethane (also, chloroform or acetonitrile) using only 5-10% excess of reagent. Although dry solvents were originally recommended, a systematic study revealed that small amounts of water are beneficial, increasing the oxidation rate as well as the yield [14). A representative procedure involving a base-sensitive oxidation product illustrates the easiness of experimental work. 

Procedures which utilize selenides are similar, but a-lithio selenides are not generally preparable via simple deprotonation chemistry, due to facile selenium-lithium exchange. - Selenium-stabilized anions are available, however, by transmetalladon reactions of selenium acetals and add readily to carbonyl compounds. The use of branched selenium-stabilized anions has been shown to result exclusively in 1,2-addidon to unhindered cyclohexenones, in contrast to the analogous sulfur ylides. The resulting 3-hydroxy selenides undergo elimination by treatment with base after activation by alkylation or oxidation (Scheme 10). An alternative method of activating either p-hydroxy selenides or sulfides toward elimination involves treatment of a chloroform solution of the adduct with thallium ethoxide (Scheme 11). A mechanism involving the intermediacy of a selenium ylide is proposed. 

A trihalo compound may be formed from the halogenation of a methyl ketone. The electron-withdrawing effect of the trihalomethyl group makes the carbonyl group very sensitive to nucleophilic addition. Consequently, in the presence of a mild base the trihalomethyl compound easily decomposes with the formation of chloroform, bromoform or iodoform, depending on the halogen. The other product of the haloform reaction is a carboxylic acid (Scheme 3.86). 

Reactions of Mn(CO) SCN with a variety of neutral ligands in chloroform yield complexes which are analogous to those prepared from MnfCO Br (4). The mode of the thiocyanato-manganese bonding in these compounds depends on the nature and position of the neutral ligand(s) present. Strong bases such as pyridine, p-toluidine (L) and 2,2 -bipyridine (L-L) give cis-disubstituted thiocyanato-N carbonyl complexes. 

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