Boron organometallic

C.R. Johnson, Sulfoximides, in D. Barton u. W.D. Ollis, Comprehensive Organic Chemistry, Bd. 3, D.N. Jones, Sulphur, Selenium, Silicon, Boron, Organometallic Compounds, S. 223, Pergamon Press, Oxford New York Toronto Sydney Paris - Frankfurt 1979. 

Jones, Sulphur, Selenium, Silicon, Boron, Organometallic Compounds, S. 237, Pergamon Press, Oxford New York Toronto. Sydney Paris Frankfurt 1979. 

As a result of the systematic application of coordination-chemistry principles, dozens of previously unsuspected stnicture types have been synthesized in which polyhedral boranes or their anions can be considered to act as ligands which donate electron density to metal centres, thereby forming novel metallaboranc elusters, ". Some 40 metals have been found to act as acceptors in this way (see also p. 178). The ideas have been particularly helpful m emphasizing the close interconnection between several previously separated branches of chemistry, notably boron hydride clu.ster chemistry, metallaboranc and metallacarbaborane chemistry (pp. 189-95). organometallic chemistry and metal-metal cluster chemistry. All are now seen to be parts of a coherent whole. 

Organometallic Complexes of Boron, Silicon, and Phosphorus Analogues of Azoles... 

The first chapter covers organometallic complexes of boron, silicon, and phosphorus analogs of azoles. This chapter continues the series by A. P. Sadimenko (Fort Hare, South Africa) in which he is treating comprehensively organometallic complexes of heterocyclic compounds. So far, he has covered, in the volumes of AHC indicated, complexes of the following heterocycles ... 

Unsolvated organomagnesium compounds have been recommended for the synthesis of organometallic derivatives of mercury, boron, aluminum, silicon, germanium, tin, phosphorus, arsenic, and antimony6-8 and have been used in procedures for the alkylation of aromatic rings and for the production of various polymerization catalysts.4 9... 

The only preparative limitation to this method is the occasional coproduction of alkenyl-boronates that presumably arise via a-elimination pathways of the ate complex generated upon addition of the organometallic reagent to the a-haloalkylboronate4,29-30. This problem is illustrated in the synthesis of 5-(rm-butyldimethylsilyloxy)-2-pentenyl-substituted dioxaborolane30. 

Thiazolinc 2 proves to be inert to organometallic attack. However, addition of organolithium and Grignard reagents to the C —N double bond of 2 can easily be achieved by previous activation with boron trifluoridc, providing /r[Pg.696]

The addition of ( )-(3-trimcthylsilylallyl)boronate (10) to the racemic oxime 9 has been used in connection with a total synthesis of cannabisativine n. The results are congruent with the application of ( )-crotylboronatc as organometallic reagent9,, 0. The reaction is anti selective and generates the diastereomeric hydroxylamines 11 and 12, where 11 is converted to a tetrahydropyridine 13, a useful intermediate for the synthesis of cannabisativine11. 

High ee values have also been obtained with organometallics," including organotitanium compounds (methyl, aryl, allylic) in which an optically active ligand is coordinated to the titanium," allylic boron compounds, and organozinc compounds. 

The synthesis of compounds containing boron-group IIB bonds also occurs by two pathways. The most convenient method is using anionic borane or carboranc species, as in the group-IB case, to react with Zn, Cd, or Hg halides. Moreover, reactions between organometallic compounds (Zn, Cd) with unchanged boranes arc also realized, so Zn and Cd decaboranes, e.g., MB H 2 n solvent (M = Zn, Cd), result from reactions of decaborane(14) with MRj . 

These compounds are the most stable of the three classes of organothal-lium(III) derivatives and have been prepared by a wide variety of classical organometallic procedures. Many exchange reactions of TIX3 (X = Cl, carboxylate) with organo derivatives of boron, mercury, tin, lead, etc., have been shown to result in formation of R2TIX compounds 73, 78), but are of relatively little preparative significance. The most frequently used procedure... 

In addition to trialkylboranes, various alkoxyboron compounds have prominent roles in synthesis. Some of these, such as catecholboranes (see. p. 340) can be made by hydroboration. Others are made by organometallic or related substitution reactions. Alkoxyboron compounds are usually named as esters. Compounds with one alkoxy group are esters of borinic acids and are called borinates. Compounds with two alkoxy groups are called boronates. Trialkoxyboron compounds are borates. 

A priori borataethenes would be expected to be much more stable than the corresponding boraethenes because, as Rundle presciently noted about organometallic structures,50 all low-lying atomic orbitals are involved in the bonding. In fact, the stabilization of 52 is the driving force for the acidity of C—H bonds of proper orientation a to tricoordinate boron. Such acidity was first detected by Rathke and Kow through the treatment of B-methyl-9-borabicyclo[3.3.1] nonane (53) with hindered lithium amides, such as lithium 2,2,6,6-tetramethylpiperidide51 (Eq. 18) ... 

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