Leonard M. Weinstock

Enantioretentive alkylation of acyclic amino acids

Abstract A stereospecific method is described for the alkylation of acyclic amino acids (alanine and phenylalanine) which proceeds with retention of configuration. The method involves a) conversion of the amino acid to the predominantly cis 2-aryl-3-carbobenzyloxy oxazolidinones (2 and 8), b) alkylation of the potassium enolate with CH3I or PhCH2Br, c) Base hydrolysis and hydrogenolysis to afford the alkylated amino acid.

Characterization of the actual catalytic agent in potassium fluoride on activated alumina systems

Abstract The spectral and chemical properties of potassium fluoride on activated alumina, an extensively used basic catalyst in organic synthesis, show that its unusually high reactivity relative to other fluoride-containing basic systems is due to the reaction of the fluoride ion with alumina to produce potassium hexafluoroaluminiate, potassium hydroxide and potassium aluminate. The reagent, more simply prepared from alumina and KOH, catalyzes the high-yielding addition of chloroform to m-nitrobenzaldehyde without producing Cannizzaro side-products.

A General, One-Step Synthesis of α-Keto Esters

Abstract Several new multi-step methods for the synthesis of α-keto esters have been reported recently which are based on the addition of alkyl lithium reagents to triethoxyacetonitrile1, the reaction of Grignard reagents with ethy1 α-oxo-1H-imidazole-1-acetate2, the alcoholysis of acy1 cyanides3, the acylation of mercaptal anions with ethy1 chloroformate4, the alkylation of 1,3-dithiane-2-carboxylate under homogeneous5 or under phase transfer conditions6 and the addition of the methyl methylthiomethyl sulfoxide anion to nitriles7. These novel methods lack the convenience of the direct addition of Grignard reagents to diethyl oxalate:

A Safer Diazotransfer Reagent

Abstract Diazotransfer reagents and reactions are achieving increasing use and prominence. While textbooks and periodicals give explicit warnings concerning diazoalkanes, the hazardous nature of related azido compounds is hardly mentioned though the widely used tosyl azide has the explosive power and impact sensitivity of tetryl1. Investigators at Dynamit Nobel have stated that pure p-tosyl azide is classified as an explosive according to German law and have, by tests, shown it to be as dangerous as TNT2.

Diarryl-a-heteroarylmalonates from Cerium(IV)-promoted Reactions of Dialkyl Malonates with Heterocyclic Compounds

Thiophenes, furans and their benzo analogs undergo facile malonylation in the 2-position on reaction with dialkyl malonate radicals generated with cerium (IV) reagent

Anodic N-dearylation of 2-azetidinones

Abstract N-Methoxyphenyl-2-azetidinones are dearylated under mild conditions via anodic oxidation.

Cyclization of electrochemically generated nitrogen radicals. A novel synthesis of 11-substituted dibenzo[a,d]cycloheptenimines

Abstract A novel and convenient synthesis of 11-substituted dibenzo[a,d]cyclo-heptimines 10 via annelatlon of electrochemically generated aminium radicals derived from substituted 5-hydroxylamino-5-methyl-5H-dibenzo[a,d]cycloheptenes 14 is described. The scope and limitations of the reaction as well as the effects of reactor design, current density and electrode material on the yield of 10 and the carbocation rearrangement by-product 28 are discussed.

Annelation of aromatic oxo compounds

Abstract The silyl enol ether of α-diazoacetoacetate is used for the annelation of aromatic oxo compounds. The method involves condensation with the oxo compound in the presence of TiCl4 followed by rhodium octanoate-catalyzed ring closure to afford furan derivatives by direct carbene isertion and β-naphthol esters by a Wolff rearrangement pathway.

The 1,2,5-Thiadiazoles

Publisher Summary This chapter presents the review of organic and physical chemistry of monocyclic 1, 2, 5-thiadiazoles up to the early part of 1967. Reference is made to the 2, 1, 3-benzothiadiazoles and related compounds only as they contribute to the chemistry of the basic ring system. The 1, 2, 5-thiadiazole nucleus is numbered as in 4. The hydrogenated forms are referred to as 1, 2, 5-thiadiazoline and 1, 2, 5-thiadiazolidine. The benzo derivatives are numbered and are named 2, 1, 3-benzothiadiazole, though much of the early literature makes use of the name piazthiole. The 1, 2, 5-thiadiazoles are very stable thermally. The unsubstituted ring is unchanged on heating at 220° and it has been reported that the potassium salt of 3-cyano-4-hydroxy-l, 2, 5-thiadiazoilse has table up to 360°. 1, 2, 5-thiadiazole generally resists electrophilic substitution. The compound is inert under various conditions of halogenation and nitration, and fails to enter the reactions with benzoyl chloride and aluminum chloride.

Cyclization of electrochemically generated nitrogen radicals. : A novel synthesis of 11-substituted dibenzo[a,d]cycloheptenimine derivatives

Abstract A novel and convenient synthesis of 11-substituted dibenzo[a,d]cyclo-heptimines 10 via annelatlon of electrochemically generated aminium radicals derived from substituted 5-hydroxylamino-5-methyl-5H-dibenzo[a,d]cycloheptenes 14 is described. The scope and limitations of the reaction as well as the effects of reactor design, current density and electrode material on the yield of 10 and the carbocation rearrangement by-product 28 are discussed.