Allyl carbonates nitrile synthesis

Allylalion of the alkoxymalonitrile 231 followed by hydrolysis affords acyl cyanide, which is converted into the amide 232. Hence the reagent 231 can be used as an acyl anion equivalent[144]. Methoxy(phenylthio)acetonitrile is allylated with allylic carbonates or vinyloxiranes. After allylation. they are converted into esters or lactones. The intramolecular version using 233 has been applied to the synthesis of the macrolide 234[37]. The /i,7-unsaturated nitrile 235 is prepared by the reaction of allylic carbonate with trimethylsilyl cyanide[145]. 

Miscellaneous Transformations. Cyanotrimethylsilane effects the transformation of acyl chlorides to acyl cyanides, a-chloro ethers and a-chloro thioethers to a-cyano ethers and a-cyano thioethers (eq 19), t-butyl chlorides to nitriles (eqs 20 and 21), 1,3,5-trisubstituted hexahydro-l,3,5-triazines to amino-acetonitriles, the cyanation of allylic carbonates and acetates (eqs 22 and 23), and the formation of aryl thiocyanates from aryl sulfonyl chlorides and sulfinates. The reagent has been used effectively in peptide synthesis and in a range of other synthetic applications. " ... 

Derivatives of Y-hydroxyacetylenic acids, which are useful intermediates in the synthesis of butenolides, are prepared from propiolic acid and ester anions. Alk-2-ynoic and 2-allenic esters are prepared by the oxidation of 3,4-disubstituted 2-pyrazolin-5-ones with lead(iv) tetra-acetate in the absence and presence of BF3 respectively. Py-Unsaturated esters are produced in high yield by the palladium-catalysed decarboxylation-carbonylation of allylic carbonates. Magnesium enolates of esters react with nitriles to give (Z)-3-amino-alk-2-enoates. Enol lactones react with diethyl methoxycarbonylmethylphosphonate to give cyclic unsaturated keto-esters (Scheme 66). ... 

A strategy based on the diastereoselective dipolar cycloaddition reaction of nitrile oxides and allylic alcoholates, has been applied to the synthesis of bis-(isoxazolines) that are precursors to polyketide fragments. These intermediates can be elaborated into protected polyols, for example, 439, by sequential chemos-elective reductive opening of each isoxazoline or, alternatively, by simultaneously, providing access to all stereoisomers of this carbon skeleton (479). 

The selective synthesis of the 2-allyltetrazoles 55 by the three-component coupling reaction of the cyano compounds 54, allyl methyl carbonate 5b, and trimethylsilyl azide 42 was accomplished in the presence of Pd2(dba)3.CHCl3 and P(2-furyl)3 (Scheme 19) [55,56]. Most probably, the formation of (r)3-allyl)( ]5-tetrazoyl)-palladium complex 56 took place through [3 + 2] dipolar cycloaddition of 7r-allylpalladium azide 44 with the nitrile 54. The complex 56 thus formed would undergo reductive elimination to form the products 55. 

Several new routes involve formation of one carbon-carbon bond in pre-formed substrates. Palladium-catalyzed cyclization of /3-hydroxyenamine derivatives has been employed in a route to substituted pyrroles and 4,5,6,7-tetrahy-droindoles with multiple substituents by formation of the C-3-C-4 bond as the key feature, as illustrated by construction of the molecule 534 (Equation 146) <2006T8533>. Zinc perchlorate-catalyzed addition of alcohols to the nitrile functionality of a-cyanomethyl-/3-ketoesters, followed by annulation gave access to a series of substituted ethyl 5-alkoxypyrrole-3-carboxylates <2007T461>. Similar chemistry has also been used for synthesis of a related set of pyrrole-3-phosphonates <2007T4156>. A study on preparation of 3,5,7-functionalized indoles by Heck cyclization of suitable A-allyl substituted 2-haloanilines has also appeared <2006S3467>. In addition, indole-3-acetic acid derivatives have been prepared by base induced annulation of 2-aminocinnamic acid esters (available for instance from 2-iodoani-lines) <2006OL4473>. 

The preparation of a-selenoketones, esters, nitriles and related compounds can easily be performed via alkylation of the corresponding enolates or stabilized carbanions [21]. These compounds have found many synthetic applications in radical chemistry. In Eq. (9), a typical example involving a ketone is depicted [22]. The stability of a-selenoketones such as 41 is remarkable. Similar reactions with lactones have been performed. For instance, this approach has been applied to the stereoselective synthesis of oxygen-containing rings to either faces of a bicyclic structure [23]. The approach based on a-selenenylation/radical allyla-tion compares favorably with classical enolate allylation procedures, which usually leads to mixture of mono- and diallylated compounds. Furthermore, this strategy is excellent for the preparation of quaternary carbon centers [24] as shown by the conversion of 43 to 45, a key intermediate for the synthesis of fredericamycin A, [Eq. (10)] [25]. Similar reactions with sulfoxides [26] and phosphonates [27] have also been reported. 

Of the five positional isomers of the four-carbon saccharinic acids theoretically possible, 3-hydroxy-2-(hydroxymethyl)propanoic acid (VI) is the only one that lacks an asymmetric carbon atom and is optically inactive and unresolvable. The first attempt at its synthesis, by Glattfeld and cowork-ers, " was by a direct method. The reaction of 2-chloro-2-deoxyglyceritol (LII) [prepared from allyl alcohol (LI) by reaction with hypochlorous acid] with cyanide ion and subsequent hydrolysis of the anticipated nitrile (LIII) should have produced the desired 3-hydroxy-2-(hydroxymethyl)-... 

The other significant variation of the prototypical Kulinkovich reaction is the so-called Kulinkovich-de Meijere reaction, where de Meijere extended the substrates from esters to amides. Other carboxylic acid derivatives including (cyclic) carbonate, imides, and nitriles also react with the key Kulinkovich intermediate. Szymoniak developed an efficient new synthesis of cyclopropanes via hydrozirconation of allylic ethers (e.g., using Cp2Zr(H)Cl) followed by addition of a Lewis acid (e.g., BFa OEta). Casey et al. further investigated the stereochemistry of this interesting cyclopropanation reaction using deuterated allylic ethers. ... 

Dilithium tetrachlorocuprate is recommended as an additive for cross coupling of Grignard compounds with tosylates even allylic and benzylic acetates give good yields . a-Methylene-ketones, -carboxylic acids and -lactones have been prepared via sulfides and sulfoxides. A convenient and general synthesis of acetylene derivatives from boranes via the reaction of iodine with lithium 1-alkynyltriorganoborates has been published ar-Nitrostyrenes can be easily obtained by a Wittig synthesis with formaldehyde in an aqueous medium . A new synthesis of unsym. ketones by reaction of dialkyldiloroboranes with lithium aldimines has recently been published . Metallo aldimines have also served for the synthesis of a variety of other compound classes such as a-hydroxyketones, a-keto acids, nitriles, and for the asym. synthesis of a-amino acids . Polycondensations of malononitriles with benzylic chlorides have been carried out quantitatively under mild conditions in dimethyl sulfoxide with triethylamine as acid acceptor . Carbonyl compounds can react with dibromoacetonitrile to yield a-bromo esters with additional carbon atom . ... 

The reaction of 2-bromo-6-lithiopyridine (13) with trialkylboranes gives intermediate boron compounds which are versatile intermediates for the preparation of unsaturated nitriles (Scheme 9). A stereospecific synthesis of dehydronerol utilizes the dianion of 3-methylbut-2-enoic acid as an isoprene functionality (Scheme 10). Lithium dianions from aj8-unsaturated acids generally undergo alkylation reactions at the a-carbon atom. In contrast the dicopper dianions undergo more selective y-alkylation (62—99%) and this ratio is generally higher than with the corresponding esters. A study of various acids and their alkylation with allyl electrophiles showed that allylic electrophiles unsubstituted at the y-carbon react... 

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