Aldehydes synthesis of homoallylic alcohols

Addition of allylmetal compounds to aldehydes synthesis of homoallylic alcohols 864... 

Brown HC, Jadhav PK (1984) S-Allyldiisocaranylborane anew, remarkable enantioselective allylborating agent for prochiral aldehydes. Synthesis of homoallylic alcohols approaching 100% enantiomeric purities. J Org Chem 49 4089 1091... 

Heteroatom-substituted allylic anions as homoenolate anion equivalents 4.5.322 Addition of ally Imetal compounds to aldehydes synthesis of homoallylic alcohols... 

Allylboron compounds have proven to be an exceedingly useful class of allylmetal reagents for the stereoselective synthesis of homoallylic alcohols via reactions with carbonyl compounds, especially aldehydes1. The reactions of allylboron compounds and aldehydes proceed by way of cyclic transition states with predictable transmission of olefinic stereochemistry to anti (from L-alkene precursors) or syn (from Z-alkene precursors) relationships about the newly formed carbon-carbon bond. This stereochemical feature, classified as simple diastereoselection, is general for Type I allylorganometallicslb. 

In 2001, the preparation of allylytterbium bromide and the synthesis of homoallylic alcohols using allylytterbium bromide were reported.39 393 Ytterbium metal was found to be activated by a catalytic amount of Mel at 0 °C in THF to produce allylytterbium bromide 66 (Equation (11)). The allylation reaction of a wide range of aromatic aldehydes and ketones proceeded at ambient temperature or less in good to high yields (Table 2). Imines also reacted with allylytterbium bromide to afford homoallyl amines (Table 3). 

Scheme 13.1. Synthesis of homoallylic alcohols by addition of allylmetal compounds to aldehydes.

The ability of allyltin halides to extend their coordination sphere allowed the preparation of chiral hypervalent complexes with diamine ligands, which have been efficient in the asymmetric synthesis of homoallylic alcohols with up to 82% ee100. Similarly, a chiral hypervalent allyltin was prepared from a low valent tin (II) catecholate, chiral dialkyl tartrate and ally lie halide101. The allylation of aldehydes and activated ketones proceeded with high enantiomeric excess. Allyltins prepared from Lappert s stannylene and allylic halides were shown to be efficient as well, although the Lewis acid character of the tin atom is much less marked in that case102,103. 

Chiral homoallylic alcohols, The glycol 1 has been used as the chiral matrbt in an enantioselective synthesis of homoallylic alcohols (4) from aldehydes and allyl-boranes (equation I). 

Addition to C=0. Hydrates of a-ketoaldehydes react selectively at the aldehyde group with allylsilanes under the influence of YbfOTfjj at room temperature. The allylation of aldehydes with allylstannanes is accelerated by benzoic acid." Another method for the synthesis of homoallylic alcohols is by the ene reaction, thus y,6-unsaturated a-hydroxy esters are obtained from glyoxylic esters at room temperature in a catalyzed process. ... 

The generation of allylic indium reagents by transmetallation of allylic stannanes with InCl3 and subsequent reaction of these with aldehydes represents an important advance for diastereoselective synthesis of homoallylic alcohols [203]. In these reactions, the stannane is added to a premixed solution of the aldehyde and InCl3 in acetone. In this way, the reaetion of cyclohexanecarboxaldehyde with the 2-butenylindium reagent affords a 98/2 antilsyn mixture of homoallylic alcohols (Scheme 10-104). 

The alkoxytitanium propene compound Ti(T] -propene)(OTr)2 (46) [153], which is believed to be generated from Ti(0 Pr)4 and two equivalents of /-PrMgCl, reacts with internal alkynes to give titanium-alkyne compounds Ti(ri-alkyne) (0 Pr)2 (47) in quantitative yield (Scheme 6.9) [154,155]. 46 reacts with carboxylic esters to produce cyclo-propan- 1 -ols in modest yields [ 156,157]. Oxidative addition of allyllic halides or allyllic alcohols to 46 proceeds readily to form allyl titanium compounds 48, whose reaction with aldehyde provides a stereoselective synthesis of homoallylic alcohols [153]. 

Admixture of alkynylstannanes, aldehydes, trimethylsilyl chloride, and InClj in acetonitrile at room temperature results in the formation of propargyl silyl ethers. In the synthesis of homoallylic alcohols, simple allylic halides can be used to form the tin halides in situ in water. ... 

Chiral compounds of this class condense with aldehydes to give a reasonable degree of enantioselective synthesis of homoallylic alcohols. Reaction of (-)-(S)-(neomenthylcyclopentadienyl) Mo(NO)Cl(Ji-syn-crotyl) 47 with benzaldehyde affords (+)-( , /f)-2-methyl-l-phenyl-3-buten-l-ol 48 with >98% ee. (+) and (-) chiral... 

The allylation of a carbonyl compound, or equivalent thereof (aldehydes, ketones, acetals, ketals, enones, acid chlorides, epoxides, etc.), performed with an allylsilane 39 promoted by a Lewis acid (TiCl, SnCl, BF3-OEt2, AICI3, EtjAlCl, etc.) is known as Hosomi-Sakurai reaction (Scheme 12.11, Eq. 1) [68, 69]. This reaction was first described in 1976, allowing the synthesis of homoallylic alcohols 43 from aldehydes and ketones 40 [70]. A year later, the authors extended the method to ketals 41, which provide homoallylic ethers 44 (Scheme 12.11, Eq. 2) [71], and to a,p-unsaturated ketones 42 (Scheme 12.11, Eq. 3) [72]. 

Ishiyama, T Ahiko, T Miyaura, N. Acceleration Effect of Lewis Acid in Allylboration of Aldehydes Catalytic, Regiospecific, Diastereospecific, and Enantioselective Synthesis of Homoallyl Alcohols. /. Am. Chem. Soc. 2002, 124,12414-12415. 

Synthesis of homoallylic alcohols through the reaction of organometallic allyl compounds with carbonyl compounds is one of the most important processes in organic synthesis. Sc(OTf)3-catalyzed allylation of aldehydes with tetraallyltin to prepare homoallylic alcohols has been reported. Recently, it was revealed that the addition of acetic anhydride to the reaction mixture dramatically increases the reaction s yields to more than 90% [10]. On the other hand, in the presence of a catalytic amount of Sc(OTf)3 (l-5mol%), benzoylhydrazines reacted with tetraallyltin to give the corresponding homoallylic hydrazines, which were readily converted to homoallylic amines (Scheme 12.6) [11]. Three-component reactions of aldehydes, benzoylhydrazine, and tetraallyltin also proceeded smoothly in the presence of a catalytic amount of Sc(OTf)3. 

Hoffmann has published full details of his diastereoselective synthesis of homoallylic alcohols from crotyl boronates (c/. 4, 149) and aldehydes (Scheme 24). In results consistent with the rationalization presented above, -boronates gave rhreo-alcohols and Z-boronates gave the erythro-diastereomer with virtually complete diastereoselectivity, i.e. threo erythro ratios in the products mirroring the E Z ratio in the starting boronates. A full account has also appeared of work by the same group on addition of chiral allylboronates such as (33) to aldehydes to produce optically active homoallylic alcohols (Scheme 25) cf. 3, 143), with approx. 70% e.e. in the case of saturated aldehydes and having the configumtion as illustrated. "... 

The synthesis of homoallylic alcohols was achieved via a Pd-catalyzed cross coupling of allyl(isopropoxy)dimethyl-silane. Similarly to the previous example (eq 84), the dimer (1) was in some cases more efficient than Pd(dba)2. The reaction of 2-methyliodobenzene was improved by using 1, and the coupling of 2-methoxyiodobenzene was only observed in the presence of 1 (eq 85). A one-pot process was optimized starting from allyl(isopropoxy)dimethylsilane and benzaldehyde. Another strategy for the preparation of homoallylic alcohols was described via a Pd-catalyzed three-component coupling of an arylboronic acid with allenes and aldehydes. 

Tetrahydropyrans hydroxylated at the 4-position have good synthetic value [113]. Although many synthetic methods have been reported [17-23,114,115], the search for potential alternate approaches and the development of eco-friendly and high-yielding reactions resulted in the development of a method that poses less problems for the environment. Synthesis of tetrahydropyranol derivatives can be achieved through the Prins-type cyclization reaction of homoallylic alcohols with aldehydes using bismuth triflate as catalyst in [bmim]PF6 solvent system [108] (Fig. 22). 

N atom of which carries a chiral substituent, react with aldehydes with high se-lectivities with formation of homoallyl alcohols of type 4, which were used in the asymmetric synthesis of complex molecules [12]. 

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