Heterosubstituted alkynes

Terminal heterosubstituted alkynes X-C=CH such as RO-C=CH [16, 17, 151-153], RSe-teCH (R= alkyl, aryl) [154-157], MejSi-teCH [158] and R P-feCH [159] were regioselectively converted into the ( )-2-ethenylzirconium complexes via hydrozirconation using 1. In marked contrast, with terminal BuTe-C=CH [154]... 

Table 5 Stereoselectivities Observed in the Hydroalumination of Heterosubstituted Alkynes by...

Even with internal alkynes, highly regio- and stereoselective hydrostannation can be observed with certain heterosubstituted alkynes. Proximal (Table 4) and halo-... 

Zanini et al. studied the atropisomerism in palladacycles derived from the chloropalladation of heterosubstituted alkynes, for example, 71. ... 

Suitably protected amino acids (112) (cysteine, serine, and lysine) have been added via the side-chain heteroatom (S, O, and N, respectively) to conjugated alkynones, alkynoic ester and alkynoic amide (113). The expected heterosubstituted vinyl product (114) was formed in each case, mainly as the ii-isomer. In an accompanying paper, this type of addition was applied to the derivatives of fluorescein, 7-hydroxycoumarin, Sudan 1, and dansyl chloride with linker arms containing a conjugated terminal alkyne. 

However, many mono-, dialkylboranes and heterosubstituted boranes (Chart 1) exhibit highly selective behavior in hydroboration of alkynes7). Thus, they appeared attractive for the controlled monohydroboration of alkynes for the synthesis of the desired vinylic boranes from terminal and internal alkynes (Eqs. 53 and 54). 

Alkenylzirconium reagents Hydrozirconation of alkynes with Cp ZifHlCl followed by reaction with iodonium salts constitutes a method for synthesis of styrenes and enynes. In the latter case it can be seen that zirconium prefers attachment to the heterosubstituted carbon atom therefore, 1,1-difiinctionalized 1-alkenes are readily prepared, including those pairing Si/Se and Te/Te. ... 

Organoboranes possessing one B—C bond in the molecule can also be obtained by hydroborating alkenes and alkynes with heterosubstituted borane derivatives, especially dihalogenoboranes, which can be stabilized by complexation with amines, phosphines, ethers and sulfides. The last two are useful complexing agents for both the preparation and the reactions of dihalogenoboranes . The most convenient synthesis of dichloroborane etherate is the reaction of LiBH. with BCl, in Et,0 ... 

PhsSiCl to give the iron silane (eq 7) Silylcuprates can be prepared by lithiation of PhsSiCl followed by treatment with cop-per(I) ion. Addition of the lithium disilylcuprate to aroyl chlorides produces the acyl silane (eq 13), while conjugate addition of the higher order silyl cyanocuprate to an alkynic morpholin-ium species was utilized for the synthesis of a heterosubstituted aUenylsilane (eq 14). ... 

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