Reactions with Group 15 hydrides

Recently, Kondo and coworkers reported on the polymerization of St with diphenyl diselenides (37) as the photoiniferters (Eq. 39) [ 162]. In the photopolymerization of St in the presence of 37a and 37b, the polymer yield and the molecular weight of the polymers increased with reaction time. The chain-end structure of the resulting polymer 38 was characterized. Polymer 38 underwent the reductive elimination of terminal seleno groups by reaction with tri-n-butyltin hydride in the presence of AIBN (Eq. 40). It also afforded the poly(St) with double bonds at both chain ends when it was treated with hydrogen peroxide (Eq. 41). They also reported the polymerization of St with diphenyl ditelluride to afford well-controlled molecular weight and its distribution [163]. 

Aminotropones have been reported through a single-step cyclization-ring expansion process from 4-aminocyclohexa-2,5-dienones (p-quinamines) bearing a 4-sulfinyl or 4-sulfonyl methyl group on reaction with sodium hydride (Scheme 62).97... 

Hydroxyl equivalent. The hydroxyl equivalent is the weight of epoxy resin containing one equivalent of hydroxyl group. It is important in calculating average molecular weights. It is determined by various methods (Lee and Nivelle, 1967), such as esterification with acids, reaction with lithium aluminium hydride, reaction with acetyl chloride and near-infra-red spectroscopy. 

In the Eqs. 58 and 59, an oxy anion provides the necessary electronic push for the 1,4-elimination to take place smoothly. In Eq. 58, this oxy anion was generated in situ by hydride reduction of the carbonyl group [27]. The in situ oxy anion generation in Eq. 59 was achieved by the cleavage of the ester group on reaction with an alkoxide ion in a protocol that is typical of transesterification [28]. 

Two new brassinosteroids could be detected from the shoots of Omithopus sativus (see. Section 2). One of them, 6-deoxo-24-epicastasterone (33), was synthesized by us from 24-epicastasterone (13) via the corresponding thioacetal 70 and subsequent reductive elimination of the thioketal group by reaction with tri-n-butyltin hydride (BujSnH) in the presence of 2,2 -azabis-2 -methylpropionitrile (A1BN) (Scheme 8).48... 

Displacement of the mesyloxy group is formally a Sn2 process. The hydride reaction with the bromo compounds probably involves electron transfer, capture of bromine, and back-donation of hydrogen (deuterium) to the substrates within the ligand sphere of the copper complexes. The reason for the dichotomy must be hinged on the acceptor characteristics of bromine vis-d-vis the harder carbon. 

Benzyl ethers of carbohydrates are formed with both primary and secondary hydroxyl groups by reaction with benzyl chloride or bromide in a strong alkaline solution of the carbohydrate. The carbohydrate is dissolved directly in the benzyl halide, containing 4.5 M potassium hydroxide, and heated to 90-100 C for several hours [13] (reaction 4.17). Sometimes the carbohydrate is dissolved in dioxane or dimethylformamide (DMF), containing 4.5 M potassium hydroxide and benzyl halide, and heated for several hours. Difficult benzylations are accomplished by dissolving the carbohydrate in DMF that was treated with sodium hydride, similar to the Hakomori reagent, followed by the addition of benzyl halide [14]. 

Synthesis by high-dilution techniques requires slow admixture of reagents ( 8-24 hrs) or very large volumes of solvents 100 1/mmol). Fast reactions can also be carried out in suitable flow cells (J.L. Dye, 1973). High dilution conditions have been used in the dilactam formation from l,8-diamino-3,6-dioxaoctane and 3,6-dioxaoctanedioyl dichloride in benzene. The amide groups were reduced with lithium aluminum hydride, and a second cyclization with the same dichloride was then carried out. The new bicyclic compound was reduced with diborane. This ligand envelops metal ions completely and is therefore called a cryptand (B. Dietrich, 1969). 

Reaction with ammonia and amines (Section 20 14) Acid an hydrides react with ammonia and amines to form amides Two molar equivalents of amine are required In the example shown only one acyl group of acetic anhydride becomes incor porated into the amide the other becomes the acyl group of the amine salt of acetic acid... 

Reactions with Salts of Main Group Mnions. Anhydrous HCl protonates the Group 15 (V) hydrides, MH, where M = N, P, and As (see Hydrides). 

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