Saturated heterocycles review

Many studies have been made of substituent effects in saturated heterocyclic six-membered rings. For a detailed discussion the review of Eliel and Pietrusziewicz should be consulted [Pg.15]

Since Eliel and Pietrusiewicz (142) have published a comprehensive review on l3C chemical shifts in saturated heterocycles, the discussion in the present report may be confined to a few basic features for the sake of completeness. It stands to reason that there is an electronegativity dependence of a-carbon chemical shifts. This was demonstrated by Lambert and co-workers (143) for a great variety of pentamethylene heterocycles, and holds also for positively charged species, such as X = (CH3)2N+, (CH3)2P+, CH3S +, Br+, and I+. The same is suggested by the good correlation of a-carbon chemical shifts in some heterocyclohexanes (143) and the a-SCS values in cyclohexanes with equatorial substituents (Figure 2)(114). 

Saturated heterocycles are important ligands. They are flexible models for the problem of competitive coordination of the hard and soft acids with the nonconjugated donor sites. Analysis of these problems is of interest for the chemistry of complex and heteroaromatic compounds. The number of publications in the 1990 s shows that the interest to the problems analyzed in the present review is still enormous. 

Bernath (92MI107) reviewed the synthesis and conformational analysis of these condensed-skeleton saturated heterocycles. 

Heterocyclic Citemistry is an annual publication which combines material previously reviewed lo thiee separate SPR volumes - Saturated Heterocyclic Chemistry, Aromatic and Heteroaromatic Chemistry and the heterocyclic sections of Organic Compounds of Sulphur, Selenium, and Tellurium. ... 

The syntheses, properties, and chemistry of heteroaromatic /J-enamino nitriles have been reviewed extensively.166 Therefore, this section deals mainly with partially saturated heterocyclic /3-enamino nitriles in addition, some further reactions of heteroaromatic / -enamino nitriles are briefly described. 

General reviews on carbenes and nitrenes in heterocyclic chemistry and on the synthesis of saturated heterocycles have been published this year, and also specific reviews on 1,2-diazepines, 1,2-benzodiazepines, thiepins, dithiepins, and aza-azulenes." ... 

Unlike lithiated tetrahydroisoquinolines, a-lithio derivatives of saturated heterocycles are configurationally stable [202-204] (review [163]), and they have a considerably higher kinetic barrier to deprotonation. Nevertheless, there have been a number of activating groups developed for the alkylation of a-lithio amines. In 1991, Beak showed that the complex of sparteine and sec-butyllithium enantioselectively deprotonates BOC-pyrrolidine, and that the derived organolithium is a good nucleophile for the reaction with several electrophiles, as shown in... 

Two further chapters deal with developments in the synthesis of saturated carbocycles (Chapter 7) and saturated heterocycles (Chapter 8) and the final chapter provides a summary of Highlights in Total Synthesis of Natural Products. A list of reviews on General and Synthetic methods is collected at the end of the Report. 

This new Specialist Periodical report combines the material previously reviewed in "Saturated Heterocyclic Chemistry", "Aromatic and Hetei oaromatic Chemistry", both of which are now discontinued, and "Organic Compounds of Sulphur, Selenium and Tellurium", which although still thriving has surrendered its heterocyclic parts but will continue to report on S-lactam antibiotic chemistry. The literature reviewed in this volume covers the period July 1978to July 1979. Brief Contents ... 

In this section, only a small portion of marketed drugs are shown to illustrate the importance of hetereocyclic chemistry in drug discovery. Many drugs containing saturated heterocycles, heterocycles with more than two heteroatoms, and non-heterocycles. In the ensuing chapters, the most popular types of heterocycles in drug discovery are reviewed for their physical and chemical properties, their constructions in the context of medicinal chemistry, and their potential liabilities as drugs when applicable. 

The decrease in size of the present volume relative to Volume 1 is mainly due to a tightening up in the presentation of the subject matter which is covered. The Reporters have attempted to achieve this end whilst still maintaining a comprehensive and a critical commentary. The decrease in size is also due to the omission of a chapter on Saturated Heterocyclic Ring Synthesis it is intended to remedy this unfortunate omission in Volume 3. We also plan to include a special review in Volume 3 covering the important recent developments in the utilization of Photochemistry in Synthesis . 

A number of reviews on several aspects of sulphur chemistry and comprehensive books on general organic chemistry include material pertinent to this Report Among these are various chapters of recent volumes of a well-known reference book and of a new comprehensive book on Organic Chemistry. A review on n.m.r. data of non-aromatic heterocyclic compounds includes numerous data on saturated sulphur heterocycles. The synthesis of saturated heterocyclic rings has been summarized. Conformations of five-membered rings have been reviewed in detail. New tellurium heterocyclic chemistry has been summarized. ... 

The aim of this Report is to review new methodology for the synthesis of saturated heterocyclic compounds. Emphasis is placed on reactions which involve a cyclization step and few ring transformations are described. Heterocycles which contain phosphorus, selenium, and silicon as the heteroatom are omitted. A few key steps in complex natural product syntheses are mentioned, but carbohydrates are excluded. The rapidly increasing numbers of reports describing the synthesis of saturated and unsaturated lactones and of crown ethers are covered in Chapters 3 and 10. 

A review of saturated, heterocyclic, three-membered rings has been published, and the literature for 1972 concerned with heterocyclic chemistry has been surveyed. The chemistry of three-membered, sulphur-containing rings has been reviewed. " The n.m.r. spectra of small-ring sulphur heterocyclic compounds and other heterocycles have been discussed. Selenium-containing cyclic compounds, including three- and four-membered rings, have been reviewed/... 

Reviews of saturated oxygen heterocycles <00JCS(P1)1291>, routes to 2,2-dimethyl-2H-[l]benzopyrans <00H(53)1193> and pyranonaphthoquinone antibiotics <00T1937>, HIV-1 active Calophyllum coumarins <00H(53)453> and of the application of (3-halovinylaldehydes in heterocyclic synthesis <00H(53)941> have appeared. 

CHEC-II(1996) covers more than 100 examples of this kind of heterocyclic compound <1996CHEC-II(8)287>. There are no specific reviews dealing directly with these heterocyclic systems. On the other hand, the saturated systems have been included in several review articles, <2004CRV2667, 2005CRV2765, 2002NPR223, 2000NPR7>. The use of some of these hetereocycles in medicinal chemistry has also been reviewed <2000BMC1213>. 

Partially and fully saturated derivatives of the following heterocyclic systems are discussed in this review ... 

This chapter describes the chemistry of the simple, nonfused 1,2,4-triazoles including those triazoles annelated by a saturated ring. A resume of the most important points discussed by Polya in the corresponding chapter in the first edition of Comprehensive Heterocyclic Chemistry (CHEC-I) <84CHEC-1(5)733> has been made and a substantial number of the earlier references have been retained, but this account will concentrate on those advances that have been made in this area since the early 1980s. A comprehensive review of 1,2,4-triazole was published in 1981 <8lHC(37)l>. 

---