3-Methallyl iodide

Treatment of p-methallyl iodide (4a X = I, Y = Me) with a silver salt gives a methallyl cation (5a Y = Me) which reacts with 1,3-dienes such as 1,3-butadiene, 1,3-cyclopentadiene or 1,3-cyclohexadiene to give the corresponding seven-membered ring compounds (20) and (21) and their isomers. However, cycloaddition of the parent allyl cation (5a) with 1,3-dienes generally produces satisfactory results. In fact, (5a Y = H) derived from allyl iodide (4a X = I, Y = H) and silver trifluoroacetate reacts with 1,3-cyclopentadiene to yield bicyclo[3.2.1]octa-2,6-diene (21 Y = H, n = 1) though in poor yield, along with... 

The chiral auxiliary is the oxazolidinone (24) derived from IS,2R) norephedrine. Acylation with propionyl chloride gives (25) and this is deprotonated to afford exclusively the internally chelated Z-enolate, which reacts with methallyl iodide from the face opposite the methyl and phenyl groups of the auxiliary. The product (26), a 97 3 mixture of diastereomers, is purified to a ratio of better than 500 1. Reductive removal of the auxiliary and careful oxidation of the primary alcohol under non-racemising conditions affords the chiral (5)-aldehyde (27). This in turn is reacted with the boron enolate of (25), which furnishes with remarkable selectivity the u aldol product (28). The reason for the choice of boron rather than lithium is to invert the facial selectivity of the reaction— the enolate is no longer constrained to be planar by internal chelation and rotates in order to place the bulky dibutyl borinyl group on the opposite side to the methyl and phenyl ... 

In Scheme 11.22 the first configuration established after the common intermediate is at C-8, which is alkylated by methallyl iodide. The observed, and desired. 

In the synthesis in Scheme 13.34, the first configuration that is established after construction of the decalin system is the one at C-8 in step A. An enolate alkylation is carried out with methallyl iodide. The observed, and desired, stereochemistry is governed by the C-10 methyl group, which blocks attack from the top side of the molecule. In step B, the five-membered ring is formed by intramolecular aldol condensation. The reduction of the enone (step C) establishes the configuration at C-13, and this chirality is subsequently transferred to C-9 by the intramolecular Claisen rearrangement in step D. 

A preliminary communication of the first synthesis by Wettstein s group (Scheme 66) was published in 1955 [131]. By this method, the atom is first introduced by etho grcarbonylation and then the C20, and C21 atoms by alkylation with methallyl iodide, and, finally, the Cg and Cxg atoms with ethoxyethnylmagnesium bromide. Ring D is formed by the intramolecular crotonic condensation of the 16,20-dicarbonyl compounds. 

The authors later successfully extended (2R,5R)-2,5-dimethylthiolane to the allylidene transfer to aldehydes. The epoxidation reaction of benzaldehyde with methallyl iodide gave the desired vinyl oxirane in 60% yield, 50 1 dr, and 86% ee. The addition of n-Bu4Nl failed to improve the yields to an acceptable level, probably due to the poor compatibility of this additive with the oxirane products [23]. 

Compound Name Mercuric Chloride Mercuric Iodide Mercuric Chloride Mercuric Ammonium Chloride Mercuric Cyanide Mercuric Cyanide Mercuric Chloride Mercuric Nitrate Mercuric Oxide Mercuric Chloride Mercuric Nitrate Mercurous Chloride Mercurous Nitrate Mercurous Chloride Mesityl Oxide Calcium Resinate Methyl Methacrylate N-Butyl Methacrylate Glycidyl Methacrylate Ethyl Methacrylate Methyl Methacrylate Methallyl Chloride Methallyl Chloride Formaldehyde Solution Methane... 

SYNTHESIS To a solution of 5.8 g of homosyringonitrile (see underESCALINE for its preparation) in 50 mL of acetone containing 100 mg of decyltriethylammonium iodide there was added 7.8 mL methallyl chloride followed by 6.9 g of finely powdered anhydrous K2C03. The suspension was kept at reflux by aheating mantle, with effective stirring. After 6 h an additional 4.0 mL of methallyl chloride was added, and the refluxing was continued for an additional 36 h. The solvent and... 

The position of the alkyl substituent in the product indicates that cyclisation occurs with rearrangement of the double bond, ie., by 1,1-elimination and formal formation and cyclisation of a vinylcarbene. Although the overall yields are not always good, the reagents are readily available and large quantities of the simple alkylcyclopropenes can be produced. 1,2-Dimethylcyclopropene has been prepared in a similar process by treatment of methallyl chloride with two equivalents of phenyl lithium, followed by quenching with methyl iodide presumably, the initial reaction leads to 1-methylcyclopropene which is converted in situ to the 2-lithio-species 10). The elimination of HBr from brominated alkylidenemalonates also leads to cyclopropenes, though in low yield U) ... 

Diels-Alder reactions are classified as [4 + 2] cycloadditions, and the reaction giving the cyclobutane would be a [2 + 2] cycloaddition. This classification is based on the number of electrons involved. Diels-Alder reactions are not the only [4 + 2] cycloadditions. Conjugated ions like allyl cations, allyl anions and pentadienyl cations are all capable of cycloadditions. Thus, an allyl cation can be a 2-electron component in a [4 + 2] cycloaddition, as in the reaction of the methallyl cation 6.2 derived from its iodide 6.1, with cyclo-pentadiene giving a seven-membered ring cation 6.3. The diene is the 4-electron component. The product eventually isolated is the alkene 6.4, as the result of the loss of the neighbouring proton, the usual fate of a tertiary cation. This cycloaddition is also called a [4 + 3] cycloaddition if you were to count the atoms, but this is a structural feature not an electronic feature. In this chapter it is the number of electrons that counts. 

Methallyl chloride or bromide as well as unsubstituted allylic halides do not work well . Nevertheless, allyl iodide and Fe(CO)s are useful starting materials for the reactions in Scheme 4 ... 

The methallyl- as well as the chloride and iodide analogs of complex XLIX are obtained in acceptable yields. ... 

Allylic chlorides, e.g., allyl, methallyl, and crotyl chlorides, are very reactive and are employed in the synthesis of unsaturaled ethers Besides the usual coupling of the sodium alcoholate and halide in alcohol solutions other conditions have been described, including reaction of the alcohol and unsaturated halide in the presence of potassium carbonate or sodium hydroxide in acetone or water. The combination of anhydrous potassium carbonate and acetone is widely used in the preparation of allyl aryl ethers the reaction is aided by the addition of finely powdered potassium iodide. ... 

The catalytic dimerization at 100 °C of butadiene (and isoprene) with dicarbonyldinitrosyliron and dicarbonylnitrosyl( r-allyl)iron [1—2 wt. %] to 4-vinylcyclohex-l-ene (CHs-substituted vinylcyclohexenes) can be carried out photochemically at —10 °C to 25 °C. It has been suggested, that intermediates formed by UV decomposition of the complexes may be the active catalysts, and that these intermediates could be the same as those produced thermally. u-Allyl iron tricarbonyl iodide was found to be ineffective as a thermal dimerization catalyst 90>. However, u-methallyl iron tricarbonyl bromide has been shown to be effective in the trimerization of isobutylene 284> [see section G2a],... 

The synthesis sequence of a Claisen rearrangement and a 1,3-cycloelimination was developed by Marc Julia, and turned out highly relevant to pyrethroid chemistry. [87] Methallyl alcohol is etherified with the methyl enol ether of methyl laevulinate. After the subsequent Claisen rearrangement, the keto-group is selectively reacted with methylmagnesium iodide. Acid hydrolysis leads to iso-pyrocine, a central building block, which is also accessible by other routes. Con-... 

Silver potassium cyanide 208-048-6 Silver cyanide 208-051-2 Cyanogen bromide 208-053-3 Cyanogen iodide 208-060-1 Guanidine nitrate 208-080-0 DL-Borneol 208-161-0 Methallyl alcohol 208-162-6... 

An optimum enantioselectivity of 90% and yield of 72% was observed for the aUyl bromide/benzaldehyde system at 5°C. In contrast to ligand 11, this new salen ligand 14 was also able to affect an enantioselective addition of aUyl iodide. Related (3-methallyl halides reacted as smoothly as the allyl halides although the enantioselectivities were lower. To demonstrate the applicability of this methodology to polyketide natural-product synthesis, p-methoxybenzyl (PMB)-protected 3-hydroxypropanal was coupled with aUyl bromide in an excellent enantioselectivity of 92%, albeit in a moderate yield of 69%. Finally, vinyl iodides and triflates were used as substrates, with 2 mol% of Ni(II) required for efficient coupling. The addition of fi-l-iodohex-l-ene to PMB-protected 3-hydroxypropanal afforded the corresponding S-allylic alcohol adduct in 75% ee. A vinyl triflate also... 

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