Boron metal stannyls

Metalated ferrocenes also serve as convenient precursors to ferrocenylboranes. Lithiated ferrocenes have been ntilized for the preparation of ferrocenylboronates FcB(OR)2 and l,T-fc(B(OR)2)2 and are especially suitable in the presence of ort/ o-directing donor-substituents. The borylation of disilylated ferrocenes with excess BCI3 on the other hand was reported to yield varying amounts of 1,3-diborylated prodnct (82 M = Fe, X = Cl) in addition to the l,F-diborylated species (83 M = Fe, X = Cl). In contrast, when 1,F-distannylated ferrocenes were treated with equimolar amounts of boron halides, l-stannyl-2-borylferrocenes (86) were formed as the major product rather than the expected... 

The compound 48 is conceptually very intersting. Boron being a strong electronaccept-ing group, 48 is in fact a push-pull ynamine. NMR data fully support the view Aminoethynyl arsines 49 are usually prepared by metal exchange from stannyl ynamines and diphenylarsenyl chloride (88)... 

Stannyl-alkali metal reagents and haioaminoboranes yield Sn—boron bonds, but the method does not include haloborazines as starting materials (Table 1). 

Cleavage of the boron—Co bond by tin halides yields Sn—boron bonds . The route supplements those involving stannyl-alkali-metal reagents and haloaminoboranes ( 5.3.17.2.2). 

Traditionally, aldol reactions were carried out under protic conditions, such that the enolate was formed reversibly (see Volume 2, Chapter 1.5). An added measure of control is possible if one uses a sufficiently strong base that the enolate may be quantitatively formed prior to addition of the electrophile. The renaissance that has occurred in the aldol reaction in the last two decades has been mainly due to the development of methods for the formation and use of preformed enolates. The simplest enolates to prepare are those associated with lithium and magnesium, and there now exists a considerable literature documenting certain aspects of lithium and magnesium enolate aldol chemistry. This chapter summarizes the aldol chemistry of preformed enolates of these Group I and Group II metals. Other chapters in this volume deal with boron enolates, zinc enolates, transition metal enolates and the related chemistry of silyl and stannyl enol ethers. 

Stannylation by transmetallation and halogen metal exchange reactions Zincation by transmetallation and halogen-metal exchange reactions Boronation by transmetallation Mercuration by hydrogen substitution Palladation by oxidative insertion Cupration... 

In a comparative study (Scheme 4) of different methods for the preparation of 2-arylthieno[3,2-fc]thiophenes 7, the lithiated species 6 was treated with zinc chloride to effect zincation, tributyl borate to effect boronation, and tri(n-bntyl)stannyl chloride to effect stannylation. Aryl bromides or iodides were nsed. The yields of the 2-aryl prodnct 7 depend on the substituents in the benzene ring, the metallated species, and the palladium catalyst,... 

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