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Olefin stannyl

The regiochemistry of the hydrozirconation of disubstituted stannyl- [24, 167-170] and silyl- [171] acetylenes and boron- [118, 172-175] and zinc- [34, 126] alkynyl derivatives result in the formation of 1,1-dimetallo compounds. Hydrozirconation of alkynyliodonium salts affords alkenylchlorozirconocenes with the Zr-C bond geminal to the iodonium moiety [176]. These zirconocene complexes allowed the preparation of ( )-trisubstituted olefins (Scheme 8-20). [Pg.265]

The fact that this reaction is stereoselective implies that the chiral triorgano-stannyl radical formed in the first step is trapped by the olefin more rapidly than it inverts. This shows the optical stability of triorganostannyl radicals, which are known to be non-planar 59) like triorganogermyl radicals 62>. [Pg.99]

The reactions did prove to be compatible with the use of a-stannyl amides. In these cases, the cyclization reaction involved the trapping of an iV-acyliminium ion by the olefin and led to the formation of substituted piperidines. [Pg.63]

Under the optimum reaction conditions, reactions of the 2-stannyl-1,3-dithiane derivatives 16,18,19 with various olefinic compounds were carried out and the results are shown in Table 3. [Pg.53]

Table 3. Reactions of 2-Stannyl-l, 3-dithiane Derivatives (16,18, 19) with Various Olefins... Table 3. Reactions of 2-Stannyl-l, 3-dithiane Derivatives (16,18, 19) with Various Olefins...
Photochemical aryloxymethylation of enones was expected to proceed by employing a-stannyl ethers in a similar fashion to stannyl sulfides. During our study, Steckhan and co-workers reported the alkoxymethylation of electron-deficient olefins with a-silyl ethers in the presence of sensitizers. On irradiation of a mixture of a-silyl ether 70 and strongly electron deficient alkene 71 in the presence of DCA and BP as sensitizers, alkoxymethyl product 72 was obtained (Scheme 29). This reaction mechanism is explained in a similar manner as mentioned in the reaction of a-silyl carbamates 57 (Scheme 24). [Pg.69]

Miura et al. built on Ryu s previous work to achieve four-component radical cascades leading to diketones (Scheme 63) [174]. This outstanding result relies on initial carbonylation of alkyl radicals to form acyl radicals, such as 196. The nucleophilicity of acyl radicals allowed them to react with electron-deficient olefins to form ct-cyano radicals (197), whose phihcity is now reversed. Thus, they were able to add onto stannyl enolates and led to ketyl radicals such as 198. Those latter radicals underwent / -elimination of trib-utylstannyl radicals. This key elimination regenerated the mediator for the initial dehalogenation. This very fine tuning of the radical reactivities is the key element that makes the whole process work. [Pg.43]

Olefination of aldehydes with a-silyl- and a-stannyl-stabilized phosphonate carbanions derived from cyclo-[L-AP4-D-Val] allow a (Z)-selective access to a,p-substituted vinyl phosphonates (343) that have been transformed into enantiomerically pure 4-alkylidene 4PA derivatives (344) (Figure 54). " Electrophilic fluorination of lithiated bis-lactim ethers derived from cyclo-[L-AP4-D Val] (345) with commercial NFSi allow direct access to a-monofluor-inated phosphonate mimetics of naturally occurring phosphoserine (346) and phosphothreonine (347), in enantiomerically pure form and suitably protected for solid-phase peptide synthesis (Figure 55). ... [Pg.355]

Recent Developments in Theoretical Organometallic Chemistry, 15, 1 Redistribution Equilibria of Organometallic Compounds, 6, 171 Redistribution Reactions of Transition Metal Organometallic Complexes, 23, 9S Redistribution Reactions on Silicon Catalyzed by Transition Metal Complexes, 19, 213 Remarkable Features of (t) -Conjugated Diene) zirconocene and -hafnocene Complexes, 24, 1 Selectivity Control in Nickel-Catalyzed Olefin Oligomerization, 17, lOS Silyl, Germyl, and Stannyl Derivatives of Azenes, N H Part I. Derivatives of Diazene, N3H2, 23, 131... [Pg.470]

Anionic nucleophiles provide valuable and versatile routes for the preparation of C-glycosides. However, the most extensively used technologies lie within the chemistry of Lewis acid-mediated reactions of carbohydrates with unsaturated hydrocarbons and derivatives thereof. In the next series of examples, reactions of sugars and sugar derivatives with olefins and their silyl-, stannyl-, and aluminum derivatives are discussed. [Pg.297]

The relationship between V(" Sn, C) and the respective dihedral angle has already been summarized in ref. [5], and new data fit readily into this concept. This is also true for the values V( Sn, C(co)) [f26] or V(" Sn, C(aikyi)) [113,114] in stannyl-substituted olefins. [Pg.115]

Members of the above class of lanthanide complexes also effect the hydro-stannylation of olefins [175]. [Pg.1003]

Hong, F.-T., Paquette, L. A. Olefin metathesis in cyclic ether formation. Direct conversion of olefinic esters to cyclic enol ethers with Tebbe-type reagents. Copper(l)-promoted Stille cross-coupling of stannyl enol ethers with enol triflates construction of complex polyether frameworks. Chemtracts t997, 10,14-19. [Pg.693]

Photoassisted electron transfer can be induced between a triaryltin chloride and an electron-rich olefin to give the organotin radical anion and then the neutral stannyl radical (equation 20-17).46... [Pg.337]

Protic-acid-catalyzed Michael additions (59) are subject to most of the limitations of base-catalyzed Michael additions (regioselectivity and stereoselectivity of enol generation, polyaddition, etc.), and hence, the stereochemistry has been little studied (60). At low temperatures silyl and stannyl enol ethers,+ ketene acetals, and allyl species are unreactive to all but the most reactive activated olefins. However, it was discovered by Mukaiyama and co-workers that enol ethers and ketene acetals react with a,/f-unsaturated carbonyl compounds in the presence of certain Lewis acids (4,61,62). Sakurai, Hosomi, and co-workers found that allylsilanes behave similarly (5,63,64). [Pg.124]

Borabicyclo[3.3.1]nonane (9-BBN) has found use in the selective hydro-boration of alkenes in the presence of other reducible functional groups and its reaction with alkynylstannates has been studied. o-Stannyl- and a-silyl-substituted crotyl-9-BBN show promise as reagents for the stereo-regulated synthesis of acyclic systems. A series of papers covers the question of olefin-alkyl exchange in. 5-alkyl-9-BBN s, " the kinetics of reduction of substituted benzaldehydes with 9-BBN, and the kinetics and mechanism of hydroboration of alkynes with 9-BBN dimers. Selective dehalogenation of tertiary alkyl, benzyl, and allyl halides in the presence of secondary or primary alkyl or aryl halides is possible with (165). The... [Pg.465]


See other pages where Olefin stannyl is mentioned: [Pg.51]    [Pg.51]    [Pg.310]    [Pg.200]    [Pg.631]    [Pg.344]    [Pg.155]    [Pg.63]    [Pg.106]    [Pg.310]    [Pg.106]    [Pg.310]    [Pg.560]    [Pg.222]    [Pg.144]    [Pg.27]    [Pg.7]    [Pg.85]    [Pg.88]    [Pg.62]    [Pg.164]    [Pg.429]    [Pg.36]    [Pg.106]    [Pg.15]    [Pg.115]    [Pg.631]    [Pg.56]    [Pg.95]    [Pg.680]    [Pg.463]    [Pg.324]   
See also in sourсe #XX -- [ Pg.51 ]




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