On the stereochemistry of the Horner—Emmons reaction between 3-functionally substituted 2-methyl-2-propenylphosphonates and aliphatic aldehydes

The reaction of diethyl 3-ethoxycarbonyl-2-methyl-2-propenylphosphonate (1a) with 3-methylbutanal (2) in heterogeneous MOH (solid)-benzene systems in the presence of 5–10 mol.% of benzyltriethylammonium chloride (BTEAC) gives the reaction product (3) with a higher, for M=K, or lower, for M=Li, ratio of 2E,4E and 2Z,4E-stereoisomers than that observed in the absence of BTEAC. Tetrabutylammonium bromide (TBAB) as a catalyst of the reaction1a + 2 3 in the system KOH (solid)-wet benzene leads to a higher [2E,4E-3][2Z,4E-3] ratio than BTEAC; this ratio grows from 4456 without TBAB to 8020 at 100 mol.% of TBAB. In the latter case the stereochemical outcome of the reaction is similar to that obtained when tetrabutylammonium hydroxide in dry benzene is used as the deprotonating agent. The corresponding diisopropyl phosphonate (1b) and 3,7-dimethyloctanal (4a) interact in the system KOH (solid)-wet benzene-TBAB to give hydroprene (5) containing 88 % of the 2E,4E-isomer (5a) while in the case of 1 equiv. of [(n-Bu₄)N]OH in dry benzene the content of5a is 92 %. Diisopropyl 3-isopropoxycarbonyl-2-methyl-2-propenylphosphonate (1c) and 7-methoxy-3,7-dimethyloctanal (4b) under either of these conditions afford methoprene (6) containing 93 % of the 2E,4E-isomer.Part 6, see ref. 1.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1094–1098, June, 1993.     

On the stereochemistry of the Horner—Emmons reaction between 3-functionally substituted 2-methyl-2-propenylphosphonates and aliphatic aldehydes

The reaction of diethyl 3-ethoxycarbonyl-2-methyl-2-propenylphosphonate (1) with 3-methylbutanal (2) in the system solid MOH (M=K, Na, Li)-benzene without phase transfer catalysts affords ethyl 3,7-dimethyl-2,4-octadienoate with the ratios of 2E,4E stereoisomer (3a) to 2Z,4E-stereoisomer (3b) of 4456, 4654, and 6040 for KOH, NaOH, and LiOH, respectively. The similar tendency is observed when DMSO is substituted for benzene, although the proportion of3a in this case is 65% with any MOH used. The reaction of1 with2 in the presence of a stoichiometric amount of a quaternary ammonium hydroxide QOH (Q=NMe₄, BnNMe₃, (n-Bu)₄N) in benzene gives higher3a3b ratios than those obtained with LiOH in the former reaction system. The increase in the content of 2E,4E-isomer3a is possibly due to the growth of the population of solvent-separated ion pairs or, generally, to the increase in the distance between the charge centers in the ionic intermediates on passing from KOH to LiOH and from [Me₄N]OH to [(n-Bu)₄N]OH. The position of the equilibrium betweenE- and Z-isomers of phosphonate1 under the reaction conditions (E-1Z-13565) is almost unaffected by the nature of the cation of the base.Part 5, see ref. 1.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1089–1094, June, 1993.     

Synthesis of nitrocyclopropanedicarboxylic acid derivatives by addition of ��-bromonitroalkanes to methylidene malonic, methylidene cyanoacetic or maleic acid derivatives

A potassium carbonate promoted addition of 2-bromonitroalkanes to methylidenemalonic and methylidenecyanoacetic acid derivatives and N-benzylmaleimide leads to the functionalized nitrocyclopropanes. In the case of less active olefins, it is reasonable to use the phase-transfer catalyst Bu₄NPF₆ (10 mol.%), whereas in the case of N-benzylmaleimide, to carry out the process in the ionic liquid [bmim]BF₄.     

Synthesis of cyclopropane-1,1,2,2-tetracarboxylic acid derivatives from aldehydes and CH-acids in the K2CO3/Bun 4NPF6/toluene heterogeneous system

A one-pot method for the synthesis of cyclopropane-1,1,2,2-tetracarboxylic derivatives was developed starting from aldehydes and cyanoacetic and 2-bromomalonic esters under heterogeneous conditions (K₂CO₃/PhMe) in the presence of recoverable phase-transfer catalyst Buⁿ ₄NPF₆.     

Reaction of citral with acetone cyanohydrin and diethylamine,and thermolysis of the resulting aminonitrile

The reactions of citral with acetone cyanohydrin and secondary amines (diethylamine, piperidine, morpholine, and N-methylaniline) to give 2-substituted amino-4, 8-dimethyl-3,7-nonadienoic acid nitriles have been examined. Possible path-ways for these reactions are discussed. The thermolysis of 2-diethylamino-4,8-dimethyl-3, 7-nonadienoic acid nitrile has been examined in solution, to give irreversibly 3-cyano-1-diethylamino-3,7-dimethyl-1,6-octadiene, this reaction proceeding faster in polar than in nonpolar solvents.The synthetic citral used contained, according to GLC, 65% of the E- and 35% of the Zisomer.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 2033–2038, September, 1989.     

Reactions of CH-acids with α,β-unsaturated aldehydes in ionic liquids

Metal carbonate-catalyzed reactions of CH-acids (diethyl malonate, ethyl acetoacetate, ethyl cyanoacetate, and ethyl 2-acetyl- and 2-ethoxycarbonyl-5,9-dimethyldeca-4,8-dienoates) with ,-unsaturated aldehydes (acrolein, crotonaldehyde, citral) were studied in an ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate [bmim][PF₆], and in a 1-butyl-3-methylimidazolium bromide ([bmim][Br]) — benzene system. The reactions with acrolein and crotonaldehyde afforded Michael addition products, those with citral resulted in Knoevenagel addition products. Sonication increased the yields of the Michael adducts. The ionic liquid [bmim][PF₆] can be recovered and repeatedly used in the reactions.     

Suzuki cross-coupling of hexachlorobenzene promoted by the Buchwald ligands

The study of cross-coupling between hexachlorobenzene and phenylboronic acid comprised five Buchwald ligands, from which 2-dicyclohexylphosphino-2′-(dimethylamino)biphenyl (DavePHOS) provided the best conversion. When excess of phenylboronic acid was used, a mixture of isomeric tri-, tetra- and pentaphenyl-substituted derivatives in the ～10:70:20 ratio was obtained, along with minor amounts of hydrodechlorination products.

     

Functionalized polychloroarenes in the Bichwald ligand-promoted Suzuki cross-coupling

Palladium-catalyzed Suzuki cross-coupling of isomeric dichloroacetophenones with phenylboronic acid in the presence of 2-dicyclohexylphosphino-2′-(dimethylamino)-biphenyl (DavePHOS, a Buchwald ligand) affords the corresponding diphenylacetophenones in high yields. The reaction of pentachloroacetophenone with phenylboronic acid (1.1–2.5 equiv.) proceeds unselectively to give isomeric mono- and disubstitution products. In the case of 3,4-dichloroanisole, 3-positioned chlorine atom is preferably replaced, however, with excess phenylboronic acid 4′;-methoxy-1,1′;:2′;,1″-terphenyl is quantitatively formed.