Organostannanes alkenes

The use of allene as a relay switch introduces the benefits/challenges of regio- and stereo-selectivity. Our initial studies of cyclization-anion capture with allene as a relay switch generated allylic amines in excellent yield. Reactions were conducted in toluene (90 °C, 20 h) in a Schlenk tube, and employed 0.5-1 atm of allene and various amines, using alkenes/alkynes as relay species (Scheme 5.6.23)." The use of organostannanes as anion-capture agents in this cascade has yet to be explored. 

Oxidations. Mildly basic conditions (NaHCOj) have been used to epoxidize alkenes. For epoxidation of water insoluble substrates, aq MeCN is a suitable medium. A very similar system is useful for oxidative cleavage of organostannanes containing a perfluoroalkyl group to furnish alcohols. a-Formylpyrroles yield 2-pyrrolinones. ... 

Cross-couplings. The Stille coupling of organostannanes with hypervalent iodine compounds has a broad scope. Diaryl and dialkenyl tellurides are also active toward alkenes if the catalytic system contains AgOAc. ... 

Couplings. Partially fluorinated allyl ketones and 1 -alkenes are formed by the Stillc coupling of P-perfluoroalkyl-substitued alkyl iodides with organostannanes with or without the presence of CO, ... 

Topics reviewed during the year include the photochemistry of indoles, sulfoxides, pyrazoles and isothiazoles, (S-hetero)cyclic unsaturated carbonyl compounds, photoinduced single electron transfer (SET) reactions of amines and of azo compounds, SET reactions of organosilanes and organostannanes with Qo and ketones, photochromic polypeptides and di(hetero)arylethenes, processes in chromophore sequences on a-helical polypeptides,aryl-aryl coupling in furans, thiophenes and pyrroles," [3+2]cycloaddition of aromatic nitriles (and esters) with alkenes, and reactions of benzylsilane derivatives. ... 

It is known that the reaction of 1,1-dibromo-l-alkenes with organostannanes affords internal alkynes [24]. The (chlorocyclopropyl)dienyne side chain 84 of callipeltoside A was prepared in 95% yield by the coupling of the 1,3-dienyl-stannane 82 with the dibromide 83. The use of DMF is important [38]. 

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