Amines from active hydrogen compounds

Free radical initiators or active hydrogen compounds such as amines or alcohols are not very effective initiators for the polymerization of lactones. Polyesters of low molecular weight are produced by these techniques. For example, copolymerization of various lactones in the presence of water at 200 °C proceeded via a hydrolysis followed by the polycondensation reaction of the hydroxy acid, giving low molecular weight products [67-69]. Low molecular weight (=10,000) tri-block copolymer (CL-b-EO-b-CL) has been prepared from e-CL and poly(ethylene glycol) (Mn=10 3) by carrying out the polymerization at 165 °C for several hours in the absence of catalysts [70]. 

Active hydrogen compounds such as alcohols, thiols, amides, urethans, and sulfonamides can be alkylated by N-vinyl-amides, -urethans, or -sulfonamides in high yields. A one-step conversion of ar. nitro compounds to isocyanates has been reported Aliphatic isothiocyanates can be prepared from amines and carbon disulfide with dicyclohexylcarbodiimide under remarkably mild conditions... 

Apparently the alkoxy radical, R O , abstracts a hydrogen from the substrate, H, and the resulting radical, R" , is oxidized by Cu " (one-electron transfer) to form a carbonium ion that reacts with the carboxylate ion, RCO - The overall process is a chain reaction in which copper ion cycles between + 1 and +2 oxidation states. Suitable substrates include olefins, alcohols, mercaptans, ethers, dienes, sulfides, amines, amides, and various active methylene compounds (44). This reaction can also be used with tert-huty peroxycarbamates to introduce carbamoyloxy groups to these substrates (243). 

Starters. Nearly any compound having an active hydrogen can be used as starter (initiator) for the polymerization of PO. The common types are alcohols, amines, and thiols. Thus in Figure 2 ROH could be RNH2 or RSH. The fiinctionahty is derived from the starter, thus glycerol results in a triol. Some common starters are shown in Table 4. The term starter is preferred over the commonly used term initiator because the latter has a slightly different connotation in polymer chemistry. Table 5 Hsts some homopolymer and copolymer products from various starters. 

The Mannich reaction consists in the condensation of formaldehyde with ammonia or a primary or a secondary amine and a compound containing at least one hydrogen atom of pronounced reactivity the active hydrogen atom may be derived from a methylene group activated by a neighbouring keto group, or from a nitroparaffin, or it may be the o- or p-hydrogen atoms in phenols. Thus when acetophenone is boiled in alcoholic solution with formaldehyde and dimethylamine hydrochloride, the Mannich base P-dimethylamino-propiopbenone hydrochloride (I) is readily formed ... 

Attempts to prepare an anhydride from 3-carboxymethylquinucli-dine-2-carboxylic acid (40) in the presence of acetic anhydride and sodium acetate led unexpectedly to the tricyclic j8-diketone (59).133 This reacts with compounds containing active hydrogen (water, alcohols, and amines) to yield 2-acetylquinuclidine-3-acetic acid derivatives (60).133... 

The reaction under consideration is typified by the formation of saturated carboxylic acids from olefins, carbon monoxide, and water. Other compounds have been used in place of olefins (alkyl halides, alcohols), and besides water, a variety of compounds containing active hydrogen may be employed. Thus, alcohols, thiols, amines, and acids give rise to esters, thio-esters, amides, and acid anhydrides, respectively (15). If the olefin and the active hydrogen are part of the same molecule, three or four atoms apart, cyclizations may occur to produce lactones, lactams, imides, etc. The cyclizations are formally equivalent to carbonylations, however, and will be considered later. 

This reaction constitutes a special type of process in which a hydrogen atom and a nucleophile are added across the diene with fonnation of a carbon-hydrogen bond in the 1-position and a carbon-Nu bond in the 4-position. Some examples of such reactions are hydrosilylation [12-18], hydrostannation [19,20] amination [21,22], and addition of active methylene compounds [21 a,23,24], These reactions are initiated by an oxidative addition of H-Nu to the palladium(0) catalyst, which produces a palladium hydride species 1 where the nucleophile is coordinated to the metal (Scheme 8-1). The mechanism commonly accepted for these reactions involves insertion of the double bond into the palladium-hydride bond (hydride addition to the diene), which gives a (jr-allyl)palladium intermediate. Now depending on the nature of the nucleophile (Nu) the attack on the jr-allyl complex may occur either by external trans-aVtBck (path A) or via a cw-migration from palladium to carbon (path B). 

N Alky] and N aryl imines have received the most attention in the literature, but significant research has also been performed in the area of "activated imines, that is, imines with electron withdrawing substituents at N. In addition to having different reactivity from N alkyl and N aryl imines, these compounds are intrinsically open to further functionalization after hydrogenation. The first of these compounds to be reduced enantioselectively were the N tosyl amines. In contrast to the related reaction with N alkyl and N aryl amines, the asymmetric hydrogenations of N tosyl amines are most often catalyzed by complexes of palladium. 

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