With NaBH

Allylic amines can be cleaved. Hydrogenolysis of allylic amines of different stereochemistry with NaBH CN was applied to the preparation of both dia-stereoisomers 655 and 657 of cyclopentenylglycine from the cyclic amines 654 and 656 of different stereochemistry[405]. 

Sodium cyanoborohydride is remarkably chemoselective. Reduction of aldehydes and ketones are, unlike those with NaBH pH-dependent, and practical reduction rates are achieved at pH 3 to 4. At pH 5—7, imines (>C=N—) are reduced more rapidly than carbonyls. This reactivity permits reductive amination of aldehydes and ketones under very mild conditions (42). 

Reduction of 2-butarione with NaBH yields 2-butanol. Is the product chiral Is it optically active Explain. 

Mehta et al. also studied the facial selectivities of 5,6-exo,eji o-disubstituted bicyclo[2.2.2]octan-2-ones 18 [75, 78]. These systems are related to the 2,3-exo,ex( -disubstituted 7-norbomanones 14, but differ in the direction of the carbonyl n face. Hydride reduction of 5,6-exo,ex( -disubstituted bicyclo[2.2.2] octan-2-ones (18) with NaBH and DIBAL-H and methylation with MeLi were smdied [75, 78],... 

Platinum was added to Nation before Incorporating CdS In order to avoid the reduction of CdS during the platlnlzatlon process. Nation (DuPont 117, 0.018 cm thick) films were soaked In Pt(NH2)2l2 (0.1 mM) solution for 4 hr. The amount of the Pt complex Incorporated was determined by measuring the optical absorption change In the liquid phase. The films were subsequently reduced with NaBH (0.1 M) solution for one day to produce Pt metal dispersed throughout the polymer film. The amount of Pt was found to be about 0.02 mg cm 2. 

To investigate this further, we probed the state of Pt before CdS incorporation into the film. After Pt incorporation and reduction with NaBH, the Pt(4f) BE was 71.1 eV, Indicating that Pt2+ complexes were completely reduced to Pt°. Pt in films without CdS can be oxidized by boiling in nitric acid as indicated by the films becoming clear. Thus, the oxidized Pt species present in fresh CdS/Pt/Nafion films is formed at some point during the CdS incorporation process. Thus, while not excluding the process proposed by Aspnes and Heller W, we consider the reduction of partially oxidized Pt as responsible, in part, for the observed induction period (10). 

Methylthiomethyl p-tolyl sulfone 257 was shown to react with various esters in the presence of excess NaH, affording compounds 263 which, upon reduction with NaBH and further treatment with alkali, can be converted to the corresponding aldehydes ". Oxidation of 263 with hydrogen peroxide gives S-methyl a-ketocarbothioates 264. ... 

An alternative synthesis of 1 through reduction of BP 7,8-dione with NaBH in ethanol has also been described (22). BP 7,8-dione was prepared from 9,10-dihydro-BP by conversion to the cis-7,8-tetra-hydrodiol by reaction with OsO followed by oxidation with DDQ (23) (Figure 4). This method entails the same number of steps as the original procedure and would appear to offer no advantage. 

Syntheses of the BA 3,4- and 8,9-dihydrodiols through reduction of the corresponding quinones with NaBH, (Figure 4) has been reported by Oesch (22,23). Attempted preparation of BA 1,2-dihydro-... 

Synthesis of DBA 3,4-dihydrodiol from DBA 3,4-dione via bro-mination and reduction of the 1,2-dibromo compound with sodium bo-rohydride has also been described (44). The DBA 3,4-dione was synthesized by Kundu from 5-bromo-2-nitro-l-naphthol in nine steps in 4.2% overall yield (45). More recently, reduction of DBA 3,4-dione with NaBH, in the presence of air has been reported to afford directly the 3,4-dihydrodiol (22). 

Anthracene is noncarcinogenic and is structurally incapable of forming a bay region diol epoxide. Anthracene 1,2-dihydrodiol is most conveniently synthesized from 2-anthranol by oxidation with phenylseleninic anhydride to anthracene 1,2-dione (55) followed by reduction with NaBH in ethanol (22) or LiAlH (55). Anthracene 1,2-dihydrodiol has also been synthesized via the Prdvost reaction route... 

Syntheses of the 1,2- and the 3,4-dihydrodiols of MBA via Methods II and IV have been described (74). The 1,2- and 3,4-diol dibenzoates of 1,2,3,4-tetrahydro-MBA prepared from MBA via the Li/-NH reduction route were readily separable by crystallization. Introduction of the olefinic bond into the 1,2-position of the 3,4-diol dibenzoate by the usual bromination-dehydrobromination procedure was complicated by the greater facility of bromination by NBS on the methyl group than the 1-position. This problem was solved (Figure 14) by allowing bromination to proceed to the dibromo stage, followed by selective reduction of the bromomethyl group with NaBH in diglyme. The monobromo derivative underwent dehydrobromination... 

The 9,10-dihydrodiol of 3-MC (24a) was synthesized from 9-hy-droxy-3-MC by Method IV (86). Oxidation of this phenol with Fremy s salt in the presence of Adogen 464, a quaternary ammonium phase transfer catalyst, furnished 3-MC 9,10-dione. Reduction of the qui-none with NaBH -C gave pure 24a in good yield. Treatment of 24a with m-chloroperbenzoic acid was monitored by HPLC in order to optimize the yield of the anti diol epoxide (25 ) and minimize its decomposition. 

Syntheses of the 1,2- and 7,8-dihydrodiols of 5-MC have been described (60,87,103). The 1,2-dihydrodiol (30a) is most efficiently prepared from l-hydroxy-5-MC (29a) by Method IV (87), with the difference that an a-phenol is employed rather than a 8-phenol as in previous examples. Oxidation of 29a with (KSO NO furnished a single isomeric quinone identified as 5-MC 1,2-aione (Figure 18). Formation of an ortho rather than a para quinone in the oxidation of an a-phenol with Fremy s reagent is unusual. Apparently the bay region methyl group serves to sterically block oxidative attack in the adjacent bay region site. Reduction of 5-MC 1,2-dione with NaBH in ethanol gave 5-MC 1,2-dihydrodiol. 

New selected possibilities created by reduction of new types of oxazines (603) in the synthesis of polyfunctional products (473, 554) are presented in Scheme 3.285. Coupling the reduction of the C=N bond with NaBH CN followed by hydrogenation of the N-0 bond or a one-step catalytic hydrogenation, and the double-bond transfer from the C(3) to the C(4) position, enables the synthesis and detection of 14 types of reduction products. In some cases, reduction is stereoselective. 

Many of the methods used for the preparation of mononuclear hydrides may be applied to the polynuclear systems. Base attack on metal carbonyls, which furnished one of the first methods for the production of carbonyl hydride species, is applicable to a wide range of carbonyls. Borohydride reduction leads to a variety of products, depending upon the reaction conditions, Os3(CO)12 reacting with NaBH in di-oxane under reflux to give, after 4 hours, a mixture of the anions [H30s4(C0)12] and [H2Os4(CO)i2]2 (79). The related reaction in tetra-hydrofuran for 1 hour yields the anion [HOs3(CO)n]- as the main product with minor amounts of the two tetranuclear anions. 

It is relevant to point out that we have recently reported [203] a similar destabilization of MgHj in a nanocomposite with NaBH synthesized by reactive mechanical milling of (Mg -i- Awt%NaBH ) where X = 2, 10 and 20. In this nanocomposite... 

Fig. 3.45 DSC traces of composites prepared with NaBH and MgH pre-milled for 5 and 20 h, respectively, and subsequently mixed for 15 min by ball milling, (a) (NaBH + 10 wt%MgH2), (b) (NaBH + 20 wt%MgH2) and (c) (NaBH + 35 wt%MgH2) (heating rate 10°C/min and argon flow rate 50 ml/min)...

The reaction of organyltellurium trichlorides with NaBH followed by the in situ treatment of the generated tellurolate with alkyl halides is a useful method to prepare several types of unsymmetrical telluride ... 

Alkyl- and aryltellurols generated in situ by the well-established reduction of ditellurides with NaBH /EtOH add to terminal acetylenes, giving (Z)-vinylic tellurides. "" ... 

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