Reactions of hydrides

Potassium hydride (KH) is a source of the strongly basic hydride ion ( H ) Using curved arrows to track electron movement write an equation for the reaction of hydride ion with water What is the conjugate acid of hydride lon ... 

Reactions of hydrides are therefore similar to those of carbonyls, and by appropriate choice of reactants a product often can be made by either route, as is shown for the mercuration of trinuclear Ru complexes ... 

Alcohols Synthesis and Reactions of Hydride-Alkyl Compounds. 40... 

DECOMPOSITION OF OsH(Ti2-H2BH2)(CO)(P Pr3)2 IN THE PRESENCE OF ALCOHOLS SYNTHESIS AND REACTIONS OF HYDRIDE-ALKYL COMPOUNDS... 

The reaction of hydride 37 with CCI4 affords the chlorostannane 41. When this reaction was followed by ORD, an initial increase in optical rotation was observed until 65-70% conversion — at which point the rotation gradually decreased to zero following first-order kinetics (equation 9)21. 

Synthesis, structure, and reactions of hydride, borohydride, and aluminohydride compounds of the /-elements.6... 

The migration reaction of hydrides to alkenes can be described as a 2+2 addition reaction. The reaction takes place in a syn fashion with respect to the alkene the two atoms M and H add to the same face of the alkene (Figure 2.8). This has been unequivocally established by experiments. Later we will see reactions where this is not the case although the overall stoichiometry is the same for both types. 

Aldehydes and ketones are reduced to 1° and 2° alcohols, respectively, by hydrogenation with metal catalysts (Raney nickel, Pd—C and Pt02). They are also reduced to alcohols relatively easily with mild reducing agent, e.g. NaBH4, or powerful reducing agent, e.g. LiAlILj. The key step in the reduction is the reaction of hydride with the carbonyl carbon. 

For paraffins and naphthenes, the important reaction of hydride ion exchange (2) is postulated, which is in turn initiated by carbonium ions derived from small amounts of thermally produced olefins in the cracking system. 

The addition reactions of hydride and several kinds of carbon nucleophiles to 125 provide an easy synthetic route to some new silatranyl j4-cyclohexadienyl complexes,... 

The reactions of hydrides and Grignard reagents with simple open-chain aldehydes and ketones 1 (L, M, S, and R being groups containing carbon and hydrogen only) are known to lead predominantly to the diastereoisomers 2 as predicted by Cram s rules (2-4). A modification of the interpretation of these experimental results was published by Cherest, Felkin, and Prudent (5). 

Selected reactions of hydride-bridged dialuminium complex 169 are presented below <20010M4301>. The reactions between complex 169 and 1 equiv of diphenylacetonitrile or benzophenone result in the bridged hydride transfer to the nitrile or carbonyl carbon atom, while those between compound 169 and 1 equiv of 3,5-diphenylpyr-azole or diphenylmethanol cause elimination of the bridged hydride ion (Scheme 3). 

SN Reactions of Hydride Donors, Organometallics, and Heteroatom- Stabilized Carbanions on the Carboxyl Carbon... 

Most SN reactions of hydride donors, organometallic compounds, and heteroatom-stabi-lized carbanions at the carboxyl carbon follow the mechanism shown in Figure 6.2. Thus, the substitution products, i.e., the aldehydes and ketones C, form in the presence of the nucleophiles. Thus, when the nucleophile and the acylating agent are used in a 2 1 ratio, alcohols F are always produced. 

Fig. 6.40. On the chemo-selectivity of the reactions of hydride donors, organometallic compounds, and heteroatom-stabilized "carbanions with acylating agents (kM t refers to the rate constant of the addition of the nucleophile to the carboxyl carbon, and kadd2 refers to the rate constant of the addition of the nucleophile to the carbonyl carbon).

For the reaction of hydride donors, organometallic compounds and heteroatom-stabilized carbanions with acylating agents or carbonyl compounds one encounters a universal reactivity order RC(=0)C1 > RC(=0)H > R2C=0 > RC(=0)0R > RC C NR It applies to both good and poor nucleophiles, but—in agreement with the reactivity/selectivity principle (Section 1.7.4)—the reactivity differences are far larger for poor nucleophiles. 

In this section as well as in Section 10.5.3, carbonyl compounds that contain a stereocenter in the position a to the C=0 group are referred to succinctly with the term oc-chiral carbonyl compound. Because of the presence of the stereocenter, the half-spaces on both sides of the plane of the C=0 double bond of these compounds are diastereotopic. In this section, we will study in detail stereogenic addition reactions of hydride donors to the C=0 double bond of oc-chiral carbonyl compounds. Additions of this type can take place faster from one half-space than from the other—that is, they can be diastereoselective. 

In this section and in Section 10.5.3, the term /J-chiral carbonyl compound will be used as an abbreviation for carbonyl compounds that contain a stereogenic center in the position fi to the C=0 group. Stereogenic addition reactions of hydride donors to /J-chiral carbonyl compounds are common, especially for substrates in which the stereocenter in the /i-position is connected to an O atom. 

First, the general mechanisms for these reactions are presented. Then the reactivity of these carboxylic acid derivatives is discussed. As expected, the factors that control the reactivity are very similar to those that affect the addition reactions of Chapter 18. Next, reactions with nucleophiles that interconvert all of the members of the carboxylic acid family are presented. Finally, the reactions of hydride and organometallic nucleophiles with these electrophiles are discussed. 

Following strategy 2 from Figure 6.32, chemoselective SN reactions of hydride-donors with carboxylic acid derivatives also succeed starting from carboxylic chlorides. For the reasons mentioned further above, weakly nucleophilic hydride donors are used for this purpose preferentially and should be added dropwise to the acylating agent in order to achieve success ... 

Neither the mechanism for all addition reactions of hydride donors to the carbonyl carbon nor the mechanism for all addition reactions of organometallic compounds to the carbonyl carbon is known in detail. It is even doubtful whether only ionic intermediates occur. For instance, for some LiAlH4 additions an electron transfer mecha-... 

Fig. 8.7. Reaction of hydride donors with norbornanone (A), norbornenone (B), and camphor (C).

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