Transmetallation organostannanes

Coleman established the hydroxypropyl stereochemistry via addition of a homochiral a-alkoxyalkyl organometallic species. This reagent was prepared in high enantiomeric excess using a Noroyi BINAL-H reduction of organostannane 33, which was transmetallated with ra-BuLi to achieve the desired organolithium reagent 35 (Scheme 7.5). Both enantiomers of 35 could be obtained via this route. 

As organotin compounds (organostannanes) undergo smooth Pd-catalysed transmetallation, aryl halides react with a wide variety of aryl-, alkenyl- and alkylstannanes [139]. Coupling with allylstannane is the first example [140]. The reaction is called the Migita-Kosugi-Stille or Stille coupling. Aryl, alkenyl, allyl, alkynyl and benzyl... 

Organostannanes, such as aryl-, alkenyl- and alkynylstannanes, are useful for the ketone synthesis via transmetallation of acylpalladium with organostannanes and... 

Oxazolidinone-Substituted Carbanions. Oxazolidinone-substituted organostannanes readily undergo transmetalation with alkyllithium reagents to the organolithium derivatives which then can undergo nucleophilic addition reactions. -Substituted oxazolidinones can act in this capacity as both a nitrogen source and source of chirality (eq 60). Although the a-stereoselection... 

Matteson and coworkers have described the deprotonation and alkylation of bis(l,3,2-dioxaborin-2-yOmethane (11). Deprotonation with LiTMP yields the stabilized anion, which can be alkylated with a variety of primary alkyl halides. Oxidation under basic conditions then unmasks the carbonyl group. Matteson has also described the deprotonation of some substituted boronic esters (12 X = SPh, SiMei). - The alkylated products derived from (12 X = SPh) can be treated with A/-chlorosuccinimide under mild basic conditions to yield either the monothioacetals or the acetals. Boron-stabilized carbanions can also be generated by transmetallation of the organostannanes. ... 

Many of the applications of organotin compounds are specific to one class of compounds (e.g. tin hydrides or allylstannanes) and these topics are covered in the corresponding chapters. On the other hand, reactions involving tin/lithium transmetallation, or palladium-catalysed coupling, can be carried out with a variety of types of organostannanes, and these reactions are collected together in this chapter. These topics have an extensive literature that is beyond the scope of this book, and the treatment here is limited to an outline of the fields, and a guide to the literature. 

Yamamoto has reported the desymmetrizing intra-molecular cyclization of the 1,3-diketone 97 for diastereoselective formation of cis-cis 98 vs. cis-trans 99. Optimized conditions with SnCU led to the jS-chelation in the synclinal arrangement 100 to give 98, whereas the use of TiCU facilitated rapid transmetalation of the organostannane yielding 99 (Scheme 5.2.22).22... 

The general mechanism for the cross coupling of organostannanes and aryl halides (the Stille reaction) is given in Scheme The transmetalation step takes place... 

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