ChemInform Abstract: Reactions of cis‐Stannyl‐boryl‐alkenes with Sulfur Bis( trimethylsilylimide) and N‐Sulfinyl(trimethylsilyl)amine ‐ X‐Ray Analysis of an 1‐Amino‐1λ4‐thia‐2‐azonia‐3‐borata‐1,4‐ cyclopentadiene.

Abstract

New heterocyclic systems ( 1-amino-lh4-thia-2-azonia-3-borata-l,4-~yclopentadienes 4a and 4 b, a lh4-thia-2-aza-3-bora-1-cyclopentanone 7 and a 1-trimethylstannyloxy-lh4-thia-2-azonia-3-borata-l,4-~yclopentadiene 8) are formed by reaction of (E)-2-diethylboryl-l-trimethylstannyl-l-butene (1 a) and (E)-3-diethylboryl-2-trimethylstannyl-2-pentene (1 b) with sulfur bis(trimethylsily1imide) (2) and N-sulfinyl(trimethylsily1)amine (3). There is a marked influence of other substituents at the C = C bond on the product distribution. It appears that all reactions proceed via an intermediate borane adduct A. In A the proximity of the electrophilic site of 2 or 3 to various reactive sites of the alkene derivative opens the way to the final products. The proposed structures are supported by consistent 'H-, "B-, 13C-, "Si-and 'lgSn-NMR data. In the case of compound 4a an X-ray analysis has been carried out.Organometallic-substituted alkenes offer numerous reactive sites for useful transformations. Organometallic substituents in cis position at the C = C bond may exert a combined influence on the reactivity of the alkene. Alkene derivatives of type 1 with cis arrangement are readily accesible by organoboration of alkynyltin compounds [']. The combined effect of substituents such as a boryl and a stannyl group is particularly attractive for studying the reactivity of 1 towards reagents which contain at least one nucleophilic and one electrophilic center (Nuc -El).In the weak borane adduct A the respective reactive centers can be in close contact. The result of the following intramolecular processes then depends mainly on R', the nature of the reagent used and, possibly, on the reaction conditions, e.g. on the solvent [2]. We have already shown that lithium amides[)], tin amides[*a3I, tin alkoxides ['] or methanolL2] are useful reagents in this respect. Similarly, new heterocyclic systems are obtained when the reagent Nuc -El is linked first to the tin atom by nucleophilic displacement of C1-(B) as shown in the reaction of sulfur diimide anions with (E)-2-chloro(dimethyl)stannyl-3-diethylboryl-2-penteneL4]. In this paper, we report on the reaction of 1 with sulfur bis(trimethylsily1imide) (2) and N-sulfinyl(trimethy1-si1yl)amine (3). In these compounds[51 the nitrogen atoms, or possibly also the oxygen atom, are the nucleophilic centers, and the sulfur atom represents the electrophilic center in NUC -El. El -NU\

Activation of Silicon- and Tin-Carbon Bonds. 1,1-Carboboration of Alkynylsilanes and -stannanes

“…These organometallic-substituted alkenes are attractive for numerous transformations, not discussed here. In Scheme 2, the various reactive sites are indicated by arrows, and some of the relevant chemistry has already been studied (Wrackmeyer, 1987;Köster et al, 1989;Wrackmeyer and Wagner, 1989;Wrackmeyer and Horchler, 1990;Wrackmeyer and Wagner, 1991;Wrackmeyer et al, 1993a The reversibility of 1,1-organoboration, indicated in Scheme 1, becomes readily apparent by warming the alkene shown in Scheme 2 (R 1 = SnMe 3 ) slightly above room temperature. Triethylborane is eliminated, and the bis (trimethylstannyl)ethyne form reacts immediately with the alkene by 1,1carboboration, transferring the alkenyl group (1,1-vinylboration).…”