Ashraf A. El-Shehawy

Enantioselective allylation of N-(trimethylsilyl)benzaldehyde imine using polymer-supported chiral allylboron reagents

Abstract Polymer-supported chiral N -sulfonylamino alcohols 3 and 4 obtained from copolymerization of enantiomerically pure amino alcohols 1c and 2c derived from (1 R )-(+)-camphor with styrene and divinylbenzene were treated with triallylborane, trimethallylborane, and tri(3,3-dimethylallyl)borane, respectively, to give polymeric allylating agents. N -(Trimethylsilyl)benzaldehyde imine was allowed to react with the polymeric chiral reagents to afford the corresponding primary homoallylamines in high yield and good enantioselectivities.

Enantioselective Synthesis of Chiral Homoallyl Alcohols and Homoallylamines by Nucleophilic Addition of an Allylboron Reagent Modified by a Polymer-Supported Chiral Ligand

Crosslinked polymer-supported chiral N-sulfonylamino alcohols 5–8 have been prepared by suspension polymerization of enantiopure N-sulfonylamino alcohol monomers 1–4 with styrene and divinylbenzene. Polymer-supported chiral allylboron reagents were prepared from the polymeric chiral ligands. Enantioselective additions of the polymer-supported allylboron reagents to aldehydes and N-(trimethylsilyl)imines have been successfully carried out in the heterogeneous system. The corresponding optically active homoallyl alcohols and homoallylamines were obtained in high yields with high enantioselectivities (up to 95% ee) which are almost the same as those obtained from homogeneous analogues. The polymer-supported chiral ligands used were recovered easily and can be reused without any loss of activity.

Enantiopure N-sulfonylamino alcohols and their copolymers as chiral auxiliaries for the highly enantioselective allylboration of aldehydes

Abstract Enantioselective synthesis of homoallylic alcohols by nucleophilic addition of chirally modified allylboron reagents to aldehydes was investigated. Reaction of enantiopure N -sulfonylamino alcohols ( 1a, 1b, 3a, 4a ) with triallylborane gave the chiral allylboration reagents. Aldehydes were converted to enantioenriched homoallylic alcohols with the reagents. Polymer-supported chiral allylboron reagents were also prepared from triallylborane and crosslinked polymers having chiral N -sulfonylamino alcohol moieties ( 5–8 ). These polymeric reagents reacted with aldehydes to give optically active homoallylic alcohols in high chemical yield with high enantioselectivities. Optical yield up to 92% ee was obtained by the use of polymeric chiral ligand 7 derived from d -camphor. The potential of this type of approach in asymmetric synthesis is discussed.

Allylation of some arylideneaminomercaptotriazinones using polymer-supported allylboron reagents and analogous allylboration reaction of imine-supported resin

Polymer-supported allylboron reagents have been prepared from triallylboranes and polymer-supported N-sulfonylamino alcohol. These polymeric reagents were reacted with arylimines to give the corresponding secondary homoallylic amines in high yields. Chloromethylated polystyrene was modified into the polymer-supported imine by the reaction with arylimines under phase transfer catalyzed conditions. This polymer was evaluated for its utilization in polymer analogue conversions. The recycleability of the polymeric ligand was also demonstrated.

Enantioselective synthesis of optically active homoallylamines by nucleophilic addition of chirally modified allylboranes to N-silylimines

Enantioselectivity in the allylboration of N-silylimines with a variety of chirally modified allylboron reagents has been examined. Optically active N-sulfonylamino alcohols (16, 17 and 19) derived from D-camphor and norephedrine were found to be efficient chiral ligands for the allylboration reagent. These reagents smoothly reacted with N-silylimines to give the corresponding homoallylic amines in a high level of enantioselectivity up to 96% ee.

Asymmetric reactions on polymers: diastereoselective allylation of polymer-supported chiral imines

Reaction of allylzinc reagent with enantiopure imine species attached to polystyrene proceeded smoothly with perfect diastereoselectivity and in excellent yield to afford polymer-supported chiral homoallylic amines.

5-Anthracenylidene and 5-(4-Benzyloxy-3-methoxy)benzylidene-hydantoin and 2-Thiohydantoin Derivatives, Synthesis, and S-Alkylation

Abstract 5-Anthracenylidene- and 5-(4-benzyloxy-3-methoxy)benzylidene-hydantoin and 2-thiohydantoin derivatives 3a-g were prepared by condensation of anthracene-9-carboxaldehyde and 4-benzyloxy-3-methoxybenzylaldehyde with hydantoin and 2-thiohydantoin derivatives. Compounds 3a, b, f undergo Mannich reaction with formaldehyde and morpholine to give the corresponding Mannich products 4a–c. For the synthesis of alkylmercaptohydantoin 5a–o, the potassium salt of compounds 3a, b, e, f were reacted with an alkylhalide, either methyl iodide, phenacyl bromide, ethyl bromo acetate, allyl bromide, or methallyl bromide, under stirring at room temperature to afford the alkylmercaptohydantoins 5a–o. Acid hydrolysis of compounds 5a–c afforded the corresponding arylidene-hydantoin derivatives 3c, d, g. 2-Methylmercapto-hydantoin derivatives 5a, c were reacted with some secondary amines such as morpholine or piperidine to afford 5-(4-benzyloxy-3-methoxy)benzylidene-2-morpholino- or piperidino glycocyamidine derivatives 7a, 5-anthracenylidene-2-morpholin-, or piperidino glycocyamidine derivatives 7b, c. Supplemental materials are available for this article. Go to the publishers online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file. GRAPHICAL ABSTRACT

Synthesis and Antimicrobial Activities of Some 6-Methyl-3-Thioxo-2,3-Dihydro-1,2,4-Triazine Derivatives

Abstract 4-Arylidene-imidazole derivatives (4a,b) were readily prepared by reacting 4-am- ino-6-methyl-3–thioxo-2,3–dihydro[1,2,4]triazin-5(4H)-one (1) with 4-arylidene-2-phenyl- 4H-oxazol-5-one (2). Reaction of 1 with some aromatic aldehydes in presence of triethylphosphite exclusively afforded the corresponding aminophosphonates 5a-c. Reaction of 1 with 3-phenyl-1H-quinazoline-2,4-dione (6a) and/or 3-phenyl-2-thioxo-2,3-dihydro- 1H-quinazolin-4-one (6b) gave 2-(6-methyl-5-oxo-3-thioxo-2,5-dihydro-3H-[1,2,4]triazin-4-ylimino)-3-phenyl-2,3-dihydro-1H-quinazolin-4-one (7). Moreover, on treating 1 with 2-phenylbenzo[d][1,3]thiazine-4-thione (8), 6-methyl-4-(2-phenyl-4-thioxo-4H-quinazolin-3-yl)-3-thioxo-3,4-dihydro-2H-[1,2,4]triazine-5-one (9) was obtained in 65% yield. Reaction of 1 with 4-sulfonylaminoacetic acid derivatives (10a,b) afforded the corresponding sulfonamides (11a,b), respectively. Acid hydrolysis of 11a afforded 7-aminomethyl-3-methyl[1,3,4]thiadiazole[2,3-c][1,2,4]triazin-4-one (12). 4-Amino-6-methyl-3-(morpholine-4-ylsulfanyl)-4H-[1,2,4]triazin-5-one (14) was prepared by reacting compound 1 with morpholine in presence of KI/I2, while 3,3′-bis(4-amino-6-methyl-5-oxo-triazinyl)disulfide (16) was obtained by oxidation of 1 with lead tetraacetate. The antimicrobial activity of the products was evaluated against Gram-positive and Gram-negative bacteria as well as the fungus Candida albicans. [Supplementary materials are available for this article. Go to the publishers online edition of Phosphorus, Sulfur, and Silicon and the Related Elements for the following free supplemental files: Additional text, figures, and tables.] GRAPHICAL ABSTRACT

Synthesis of novel bicycloalkane ring-fused pyridines via Michael addition reaction of a,ß-Unsaturated Nitriles

Camphorylidene(cyano)thioacetamide (3) and camphorylidenemalononitrile (9) were easily prepared by the reaction of (+)-camphor (1) with cyanothioacetamide (2) and malononitrile (8), respectively, under solid-liquid phase-transfer catalyzed conditions. The reaction of the arylidene derivatives of malononitrile, cyanothioacetamide and cyanoacetamide with 3 and 9 leads to condensed 2-thioxo- and 2-oxo-pyridine derivatives. Treatment of the latter compounds with P4S10 causes transformation into the corresponding pyridinethiones.