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

Studies on n-(alpha-chlorobenzylidene)carbamoyl chloride part 2, reaction of n-(alpha-chlorobenzylidene)carbamoyl chloride with active methylene compounds

A new process of multiple sequence of the Diels-Alder reaction, referred to as “diene-transmissive Diels-Alder reaction”, of cross-conjugated trienes, and a stepwise sequence of double Diels-Alder reaction of cross-conjugated triene equivalents are presented. Bis (silyoxy) cross-conjugated trienes, 1 and 2, undergo two sequential Diels-Alder reactions with a variety of dienophiles giving hydronaphthalene rings. Some characteristics of this reaction have been discussed in terms of stereo-, regio-, and chemoselectivity.Next, cross type of diene-transmissive Diels-Alder reaction has been demonstrated by using trienes, 1 and 2. The first cycloaddition stage of cross reaction, which has to be highly selective in the formation of mono-cycloadducts, has been performed by the reaction of active triene 2 with cyclic olefins or both the trienes, 1 and 2, with acyclic olefins. The second cycloadditions with a variety of dienophiles afforded cross type of bis-adducts. In the similar reactions of 2-ethoxy substituted 34 and 1-methyl substituted cross-conjugated triene 36, the initial cycloaddition selectively occurs across mono-substituted diene part in 34 and disubstituted one in 36, respectively.Finally, cross types of stepwise sequential Diels-Alder reactions in a one-pot procedure are presented using the triene equivalents, 33, 35, 55, and 63. Among them, diene-alcohols, 55 and 63, are very useful triene equivalents, as they are readily available from the Grignard reaction of chloroprene. It is particularly noteworthy that the sequential Diels-Alder reaction using 63 provides a new method for the two six-membered rings annelation to cyclic ketones : Naphtho-annelated cycloalkanes with a variety of unsaturation are obtained by choosing the kind of dienophiles, the order of their use, and dehydrogenation.

Diene‐Transmissive Diels‐Alder Reactions and Their Related Reactions

Michael addition of organomagnesiums or -lithiums with methyl 2-(trimethylsilyl)propenoate leads to either 1:1 or 1:2 adduct anions, depending upon the reaction conditions and the reactivity of donor molecules. The adduct anions, both 1:1 and 1:2 types, are quenched with alkyl halides or water in a highly stereoselective manner to produce α-silylated esters. A rigid intramolecular chelation working in the adduct anions is partly responsible for the high selectivity.

A Michael Addition and Alkylation Sequence Using Methyl 2-(Trimethylsilyl)propenoate. Stereoselective Synthesis of α-Silyl Esters.

Benzothiazolium N-phenacylide reacted with methylenecyclopropenes having an acyl group on the 4-position to give 3a,11a-dihydro-5aH-furo[3′,2′:2,3]pyrido[6,1-b]benzothiazole derivative via an intermediary 3-butadienylbenzothiazolium betaine. The reaction of the ylide with a methylenecyclopropene bearing two cyano groups on the 4-position in THF gave a cyclobutane together with benzothiazole, whereas a 3-butadienyl-2-ethoxybenzothiazoline derivative was obtained in the reaction in EtOH.

Otohiko Tsuge

Papers

Studies on n-(alpha-chlorobenzylidene)carbamoyl chloride part 2, reaction of n-(alpha-chlorobenzylidene)carbamoyl chloride with active methylene compounds

Diene‐Transmissive Diels‐Alder Reactions and Their Related Reactions

A Michael Addition and Alkylation Sequence Using Methyl 2-(Trimethylsilyl)propenoate. Stereoselective Synthesis of α-Silyl Esters.

Novel reactions of benzothiazolium n-phenacylide with methylenecyclopropenes

Synthesis of (Diethoxyphosphoryl)acetonitrile Oxide and Its Cycloaddition of Olefins. Synthetic Applications to 3,5-Disubstituted 2-Isoxazolines.