The recent advances in nanotechnology and the corresponding increase in the use of nanomaterials in products in every sector of society have resulted in uncertainties regarding environmental impacts. The objectives of this review are to introduce the key aspects pertaining to nanomaterials in the environment and to discuss what is known concerning their fate, behavior, disposition, and toxicity, with a particular focus on those that make up manufactured nanomaterials. This review critiques existing nanomaterial research in freshwater, marine, and soil environments. It illustrates the paucity of existing research and demonstrates the need for additional research. Environmental scientists are encouraged to base this research on existing studies on colloidal behavior and toxicology. The need for standard reference and testing materials as well as methodology for suspension preparation and testing is also discussed.

Nanomaterials in the environment: Behavior, fate, bioavailability, and effects

Since the discovery of organic azides by Peter Griess more than 140 years ago, numerous syntheses of these energy-rich molecules have been developed. In more recent times in particular, completely new perspectives have been developed for their use in peptide chemistry, combinatorial chemistry, and heterocyclic synthesis. Organic azides have assumed an important position at the interface between chemistry, biology, medicine, and materials science. In this Review, the fundamental characteristics of azide chemistry and current developments are presented. The focus will be placed on cycloadditions (Huisgen reaction), aza ylide chemistry, and the synthesis of heterocycles. Further reactions such as the aza-Wittig reaction, the Sundberg rearrangement, the Staudinger ligation, the Boyer and Boyer-Aube rearrangements, the Curtius rearrangement, the Schmidt rearrangement, and the Hemetsberger rearrangement bear witness to the versatility of modern azide chemistry.

Organic Azides: An Exploding Diversity of a Unique Class of Compounds

Asymmetric 1,3-Dipolar Cycloaddition Reactions

One of the initial steps in the development of therapeutic agents is the identification of lead compounds that bind to the receptor or enzyme target of interest. Many analogs of these lead compounds are then synthesized to define the key recognition elements for maximal activity. In general, many compounds must be evaluated in both the lead identification and optimization steps. Increasing burdens have been placed on these efforts due to the large number of new therapeutic targets that continue to be identified thorough modern molecular biology methods.1 To address this demand, very powerful chemical and biological methods have been developed for the generation of large combinatorial libraries of peptides2 and oligonucleotides3 that are then screened against a receptor or enzyme to identify high-affinity ligands or potent inhibitors, respectively. While these studies have clearly demonstrated the power of library synthesis and screening strategies, peptides and oligonucleotides generally have poor oral activities and rapid in vivo clearance;4 therefore their utility as bioavailable therapeutic agents is often limited. Due to the favorable pharmacokinetic properties of many small organic molecules (<600-700 molecular weight),5 the design, synthesis, and evaluation of libraries of these compounds6 has rapidly become a major frontier in organic chemistry. Lorin A. Thompson was born in Lexington, KY, in 1970. He received the Bachelor of Science degree from the University of North Carolina, Chapel Hill, in 1992 where he worked under the guidance of Joseph Desimone. He is currently pursuing his doctorate in the laboratory of Jonathan Ellman at UC Berkeley where he is the 1994 Glaxo-Wellcome fellow. His research interests include the development of synthetic methodology for organic library construction.

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Synthesis and Applications of Small Molecule Libraries.

1,2-Amino Alcohols and Their Heterocyclic Derivatives as Chiral Auxiliaries in Asymmetric Synthesis

Nucleophilic substitution of 4,7-dichloro-3,8-diphenyl-1,2-diazocine with succinimide, phthalimide, N-methyl-p-toluenesulfonamide, and o-benzosulfimide, in the presence of silver oxide, gave the corresponding 4-mono(imido)- and 4,7-di(imido)-1,2-diazocines. 4-Acetoxy-7-phthalimido- and 4-phenylthio-7-phthalimido-1,2-diazocine were also prepared. Thermolysis of the mono(imido)-1,2-diazocines in xylene under reflux afforded the corresponding di(imido)-1,2-diazocine and/or five pyridine derivatives, whose relative yields depended upon the nature of imido substitutents in the diazocines. However, 4,7-di(imido)-1,2-diazocines did not decompose in xylene under reflux. Thermolysis of 4,7-bis(phthalimido)-1,2-diazocine at 300–310 °C gave 3,6-bis(phthalimido)-2-phenylpyridine with the extrusion of benzonitrile. In the thermolysis of the acetoxy(230–240 °C) or phenylthio-substituted 1,2-diazocine (240–260 °C), 6-acetoxy- and 6-benzoyl-3-phthalimido-2-phenylpyridine, or 6(and 3)-phenylthio-3(and 6)-phthalimido-2-phe...

Synthesis of Arylthio-Substituted 3,8-Diphenyl-1,2-diazacycloocta-2,4,6,8-tetraenes and Their Thermolysis

A new synthetic method of 2-(1-phosphorylalkyl)furans with a variety of substituents on the ring is presented. Cycloaddition of (diethoxyphosphoryl)acetonitrile oxide to O-protected allyl alcohols is followed by a simple sequential procedure including Raney Ni reduction and acid treatment to give 2-(1-phosphorylmethyl)furans. The phosphorus-stabilized carbanions derived from the phosphorus-functionalized furans are applied to alkylation, oxidation with oxygen, or olefination to provide 2-(1-phosphorylalkyl)furans, 2-acylfurans, or 2-(1-alkenyl)furans, respectively. Some other synthetic applications are also described.

Synthesis of 2-(1-Phosphorylalkyl)- and 2-(1-Alkenyl)furans through Nitrile Oxide Cycloaddition Route

A cross-conjugated triene, trans-3-methylene-1,4-hexadiene, is accessible from the Grignard reagent of chloroprene and methyloxirane via 1-methyl-3-methylene-4-pentenyl tosylate. The diene-transmissive Diels–Alder reaction of the triene and the stepwise sequence of double Diels–Alder reaction of the tosylate are investigated. Stereo- and regioselectivity of these reactions in the presence or absence of Lewis acid catalyst are discussed.

Double Diels-Alder Reaction of trans-3-Methylene-1,4-hexadiene and 1-Methyl-3-methylene-4-pentenyl Tosylate

Thermally stable trimethylsilylmethyl azide was first synthesized from the reaction of chloromethyltrimethylsilane with sodium azide. Its use as an α-functionalized synthetic equivalent of methyl azide was demonstrated in the reaction with acetylenic dipolarophiles and the subsequent reaction of the cycloadducts with aldehydes and water in the presence of fluoride ion.

A silyl-functionalized alkyl azide, trimethylsilylmethyl azide; synthesis and cycloaddition reaction to acetylenic dipolarophiles

La premiere etape de cycloaddition de la reaction croisee, qui est fortement selective vis-a-vis de la formation de monocycloadduits, est realisee par reactions d'un triene active avec des olefines cycliques ou celles de trienes avec des olefines acycliques. Les secondes cycloadditions avec une variete de dienophiles conduisent a des bis-adduits de types croises

Otohiko Tsuge

Papers

Synthesis of Arylthio-Substituted 3,8-Diphenyl-1,2-diazacycloocta-2,4,6,8-tetraenes and Their Thermolysis

Synthesis of 2-(1-Phosphorylalkyl)- and 2-(1-Alkenyl)furans through Nitrile Oxide Cycloaddition Route

Double Diels-Alder Reaction of trans-3-Methylene-1,4-hexadiene and 1-Methyl-3-methylene-4-pentenyl Tosylate

A silyl-functionalized alkyl azide, trimethylsilylmethyl azide; synthesis and cycloaddition reaction to acetylenic dipolarophiles

Diene-transmissive Diels-Alder cycloaddition reaction of bis(silyloxy) cross-conjugated trienes