Allyltin, with derivatives

Allylcyciohexanone, 42,14 Allyllithium, 41, 30 from allyltin derivatives, 41, 32 reaction with 4-methyl-2-pentanone, 41,30... 

Allyl silanes react with epoxides, in the presence of Bp3-OEt2 to give 2-allyl alcohols. The reaction of a-bromo lactones and CH2=CHCH2Si SiMe3)3 and AIBN leads to the a-allyl lactone. " Benzyl silanes coupled with allyl silanes to give ArCH2—R derivatives in the presence of VO(OEt)Cl2 " and allyltin compounds couple with allyl silanes in the presence of SnCU. " Allyl silanes couple to the a-carbon of amines under photolysis conditions. ... 

Pd-catalyzed intramolecular etherification reactions of aliphatic alcohols have also been practiced in tandem with other bond-forming processes, such as a Pd-catalyzed allyltin addition to an aldehyde (Equation (32)).160 Similarly, a tandem C-N and G-O bond formation sequence occurs (Equation (33)) during the reactions of /3-amino alcohols with biscarbonates in the presence of the N,O-acetal-derived ligand 43.161-163... 

Scheme 7-16 shows that a similar synthetic route leads to the asymmetric synthesis of optically active 62. The synthesis that began from homochiral aldehyde (—)-52 used this newly discovered asymmetric epoxidation three times, 52 —> 58, 58 —> 68, and 68 —> 61, finishing the conversion from 52 to 61 by following a shortened route. The last chiral center to be built is C-27, and the addition of allyltin to the aldehyde derived from 61 proceeds with high stereoselectivity to give the chiral aliphatic segment 62. 

An interesting approach to carbobicyclic polyhydroxylated compounds was proposed by Jarosz.43 It was based on a Lewis acid transformation of sugar allyltins 82 into dieno-aldehydes 83 with the fi-geometry across the internal double bond exclusively. The Wittig-type reaction of 83 afforded a triene, which underwent cyclization under high pressure, providing derivatives of bicyclo[4.3.0]nonane 84. Alternatively, dienoaldehyde 83 was converted into the phosphonate 85, which afforded the bicyclo[4.4.0]-decene derivatives (86) upon reaction with an aldehyde and simultaneous cyclization of the resulting triene.43 (Fig. 29). 

Tin(IV) halide-catalysed reactions of 4-, 5-, and 6-alkoxy(alk-2-enyl)stannanes exhibit 1,5-, 1,6-, and 1,7-asymmetric induction, respectively. For example, 4-substituted (pent-2-enyl)stannanes (56) give e-hydroxy derivatives (57) with a syn anti ratio of >30 for hydroxy and benzyloxy substrates (i.e. R = OH, OCH2Ph). A key allyltin trichloride intermediate has now been identified, and the transition states for its reaction with aldehyde have been calculated as being over lOkcalmol" apart for the alternative product stereochemistries. ... 

Radical chain reactions can take place via organotin reagent without hydrogen donors such as allyltin [38, 39]. This methodology has been applied to synthesize some important chiral precursors of natural products (for example pseudomonic acid). Thus, the pentose derivative 35 affords the compound 36 with retention of configuration via the carbohydrate radical R- at C-4 position [Scheme 18]. 

In 1995, Porter et al. [34] reported the first excellent results for free radical addition to an electron-deficient alkene by use of chiral zinc complexes. Reaction of the oxa-zolidinone 9 with tert-butyl iodide and allyltributylstannane 30 in the presence of Zn(OTf)2 and a chiral bis(oxazoline) ligand 12 gave the adduct 44 in 92 % yield with 90 % ee (Sch. 18). The chiral bis(oxazoline) complexes derived from ZnCl2 or Mg(OTf)2 gave racemic products. In this reaction, lower allyltin/alkene ratios gave substantially more telomeric products, and a [3 + 2] adduct 45 of the oxazolidinone 9 and the allylstannane 30 was obtained at temperatures above 0 °C. 

Sugar allyltin derivatives are very useful synthetic intermediates. The most convenient and reliable method for their preparation is a so-called xanthate procedure. The first compound of this class was prepared in 1988 by Mortlock and Thomas [74]. 1,2-0-isopropylidene-D-glycer-aldehyde (80) was converted into allylic alcohol and further transformed into the corresponding xanthate 81. This compound underwent thermal [3,3] rearrangement into the dithiocarbon-ate 81a, which upon reaction with tri-n-butyltin hydride provided the final sugar allyltin 82 as a mixture of isomers with the E-one strongly predominating (O Scheme 35). 

Allyl sulfones have been used in a large number of valuable syntheses, but notably in the synthesis of alkenes, dienes and polyenes. Thus a-alkylallyl tolyl sulfones afford terminal alkenes regioselectively when treated sequentially with 2 equiv. of tin hydride and concentrated hydrochloric acid (Scheme 117, entry Allyltin derivatives, which are intermediates in this transformation, can be isolated if the acidic treatment is omitted (Scheme 117, entry a). 

Table 6.3.2 Reactions of allyltin derivatives with DEAD in Et20 (half-lives of reactions for 0.0254 mol dm solutions)...

The effect of added LiC104 was studied with five allyltin derivatives in ether, under standard conditions." The results are given in Table 6.3.4. In pure ether, the yields of the studied compounds after 3 h were less than 5%. The yield for allyldi-n-butyltin chloride was equal to 30%. Illumination for a longer time led to decomposition. The addition of 4 mol dm of LiC104 produced a considerable increase in the yield of the reaction no cycladdition products were detected, and the ratio of the M-ene and H-ene reactions varied from ca. 1 1 for allyltricyclohexyltin to 1 0 for allyltriphenyltin. As observed with the azo enophiles, an increase in the polarity of the medium resulted in an increase in the overall rate of the reaction, and a chemoselectivity favoring the M-ene reaction. 

Table 6.3.4 Reaction of allyltin derivatives with singlet oxygen in 4 mol dm solution of UCIO4...

Trost and coworkers developed a chiral zinc phenoxide for the asymmetric aldol reaction of acetophenone or hydroxyacetophenone with aldehydes (equations 62 and 63) . This method does not involve the prior activation of the carbonyls to silyl enol ethers as in the Mukaiyama aldol reactions. Shibasaki and coworkers employed titanium phenoxide derived from a phenoxy sugar for the asymmetric cyanosilylation of ketones (equation 64). 2-Hydroxy-2 -amino-l,l -binaphthyl was employed in the asymmetric carbonyl addition of diethylzinc , and a 2 -mercapto derivative in the asymmetric reduction of ketones and carbonyl allylation using allyltin ° . ... 

In Section 12.7.B, the Stille coupling reaction reacted a vinyl tin compound with a vinyl triflate, in the presence of palladium(O). Tetravalent tin complexes add to aldehydes and ketones, in the presence of a Lewis acid. Allyltin complexes are, by far, the most widely used of these compounds.297 a typical example is taken from the work of Keck, in which a chiral aldehyde (455) was treated with allyltributyltin, in the presence of various Lewis acids. S As shown in Table 12.19, a mixture of syn (456) and anti (457) products was obtained. The ratio of 456/457 was dependent on the structure of the R group in 455, the solvent and the Lewis acid.The anti product (457) was obtained by using the tert-butyldimethylsilyloxy derivative (sec. 7.3.A.i) of 455 with 2 equivalents of boron trifluoride in dichloromethane. The syn product is obtained preferentially when the benzyloxy derivative of 455 is used with titanium tetrachloride in dichloromethane.298... 

Reaction of aldohexofuranose 5,6-diols with TPP/imidazole/l2 has afforded the corresponding 5,6-unsaturated derivatives, while elimination of HBr from the 6-bromo compound 23, followed by hydroboration, has generated the product 24 with the L-ido configuration (Scheme 4). Some sugar allyltin derivatives (e.g. 

---