Diamines Experimental Procedure

Annual Volume 71 contains 30 checked and edited experimental procedures that illustrate important new synthetic methods or describe the preparation of particularly useful chemicals. This compilation begins with procedures exemplifying three important methods for preparing enantiomerically pure substances by asymmetric catalysis. The preparation of (R)-(-)-METHYL 3-HYDROXYBUTANOATE details the convenient preparation of a BINAP-ruthenium catalyst that is broadly useful for the asymmetric reduction of p-ketoesters. Catalysis of the carbonyl ene reaction by a chiral Lewis acid, in this case a binapthol-derived titanium catalyst, is illustrated in the preparation of METHYL (2R)-2-HYDROXY-4-PHENYL-4-PENTENOATE. The enantiomerically pure diamines, (1 R,2R)-(+)- AND (1S,2S)-(-)-1,2-DIPHENYL-1,2-ETHYLENEDIAMINE, are useful for a variety of asymmetric transformations hydrogenations, Michael additions, osmylations, epoxidations, allylations, aldol condensations and Diels-Alder reactions. Promotion of the Diels-Alder reaction with a diaminoalane derived from the (S,S)-diamine is demonstrated in the synthesis of (1S,endo)-3-(BICYCLO[2.2.1]HEPT-5-EN-2-YLCARBONYL)-2-OXAZOLIDINONE. 

The experimental procedure is based on the removal of coordinated carbonate by the addition of hydrochloric acid to form the diaqua complex, with subsequent coordination of the diamine. Excess acid is used to inhibit isomerization... 

Our interest in the synthetic utility of N-chelated organolithium compounds was prompted by this early work. Since detailed experimental procedures were not generally available at that time, we initiated a study of the effects of time, temperature, stoichiometry, etc., on the reactions of BuLi-TMEDA with benzene. We found that optimum metalation of benzene occurs when the preformed BuLi-TEMEDA complex, prepared from equimolar amounts of the organolithium reagent and diamine, is... 

At,At-Di-tert-butyl diamine (3), lithium, THF, HSiCls, n-hexane. Experimental procedure... 

The next method Strike has for semi-direct amination is really weird, Strike is really exposing Strike s ignorance of chemistry with this dog. But if one looks hard at the articles cited, the potential is there. The authors came up with this little procedure that produced vicinal diamines out of alkenes [83]. Later they found that if they did a couple of things different, they would end up with a monoamine with the majority product being at the beta carbon. The following is a conjoining of the two paper s experimentals ... 

In the future, further studies should be addressed to improve the chemose-lectivity and diastereoselectivity of the reductive coupling process, especially searching for novel reagents and milder experimental conditions. As a matter of fact, a few novel reductive couphng procedures which showed improved efficiency and/or stereoselectivity have not been further apphed to optically active imines. For example, a new electrochemical procedure which makes use of the spatially addressable electrolysis platform with a stainless steel cathode and a sacrificial aluminum anode has been developed for imines derived from aromatic aldehydes, and the use of the N-benzhydryl substituent allowed 1,2-diamines to be obtained with good yields and dl-to-meso ratios... 

Evaporation of the mother liquor and treatment of the residue under similar experimental conditions afforded ( )-(—)-34 in a yield of 57% with an optical purity of 62%. Optically active threo-1,2-diamino-1,2-diphenylethane was also an effective diamine for the optical resolution of racemic 34 that was obtained in a yield of 78% with an optical purity of 92% [70]. As previously described, the optical resolution of racemic trans-1,2-cyclohexanediol could be performed under similar experimental conditions [27]. Notably, this procedure was found effective also for the optical resolution of hydroxy oximes. Thus, when equimolar amounts of racemic ( )-l,2-diphenyl-2-(hydroxyimino)ethanol (50) and (R,R)-29 were added to benzene and crystallized, (7 )-(—)-( )-50 was recovered in a yield of 56 % based on the enantiomer in the racemate (Scheme 24) [27]. 

Plastification phenomena at higher temperature (150 C) described above for pure vernonia oil have been observed here for vernonia B-staged materials as well, if the solubility parameters of the epoxy matrix and vernonia rubbery phase are similar. Such formulations are based on less polar diamines for example, the mixture of epoxy resin, DAPM, and vernonia B-staged material. The plastification in this case has been avoided by a two-step curing procedure (see the experimental section). The general rule is to carry out the epoxy resin cure at a lower temperature and build the rigid matrix, then to increase the temperature and cure the less reactive vernonia epoxy groups with the excess of diamine into rubbery particles and simultaneously post-cure the matrix. 

Plastification phenomena, however, are not observed for formulations based on more polar diamines (than DAPM), for instance, DDS. In this case, the solubility parameters of the "polar" epoxy matrix and "nonpolar" vernonia phase are quite different. DDS based formulations, therefore, do not require a two-step curing procedure in order to build the molecular weight of the matrix at lower temperature. They form two-phase thermosets directly at 150 C (see Experimental section). 

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