Oxazolidine-2-thione heterocycles

Among chiral auxiliaries, l,3-oxazolidine-2-thiones (OZTs) have attracted important interest thanks to there various applications in different synthetic transformations. These simple structures, directly related to the well-documented Evans oxazolidinones, have been explored in asymmetric Diels-Alder reactions and asymmetric alkylations (7V-enoyl derivatives), but mainly in condensation of their 7V-acyl derivatives on aldehydes. Those have shown interesting characteristics in anti-selective aldol reactions or combined asymmetric addition. Normally, the use of chiral auxiliaries which can accomplish chirality transfer with a predictable stereochemistry on new generated stereogenic centers, are indispensable in asymmetric synthesis. The use of OZTs as chiral copula has proven efficient and especially useful for a large number of stereoselective reactions. In addition, OZT heterocycles are helpful synthons that can be specifically functionalized. 

Chiral thiazolidine-2-thiones and oxazolidine-2-thiones. E. Fujita and Y. Nagao, Adv. Heterocycl. Chem., 45, 1 (1989). 

A useful diastereoselective synthesis of aldols using chiral 3-acyl-1,3-oxazolidine-2-thiones 30, 31, 34, and 35, was developed. As described in Section II, (4/ ,5S)-MPOT (5) and (4S)-EOT (2) were prepared. These chiral heterocycles were employed as chiral auxiliaries. As enolating reagents, tin(II)... 

The C4-chiral thiazolidine-2-thiones and oxazolidine-2-thiones developed by us proved to be efficient for chiral induction. They should be applicable to practical syntheses of drugs. Novel chiral designs using these functional and chiral heterocycles seem likely in the future, especially when used in combination with organometallic reagents and/or molecular symmetry. Creative investigations employing such chiral heterocycles and related compounds will be extensively pursued. 

Abstract The high synthetic versatiUty exhibited by the isothiocyanato motif has allowed its use as a building block in the preparation of a plethora of derivatives. When present in carbohydrates, the strong electrophilicity shown by isothiocyanates, together with the possibility of undergoing cycloaddition reactions has made it possible to access a broad spectrum of heterocyclic compounds, of either synthetic or pharmaceutical interest. Among them, noteworthy are 1,3-oxazolidine- and l,3-oxazinane-2-thiones (cyclic thiocarbamates), 2-amino-2-oxazolines (cyclic isoureas), 2-amino-2-thiazolines (cyclic isothioureas), nucleosides, and spironucleosides. 

A large number of azomethine nitrofurans containing various heterocyclic rings have been synthesized the most impKjrtant of these contain either a hydantoln Table 6.5) or oxazolidinone Table 6.6) ring. Nitrofurans containing the following rings have also been studied 3-oxazolidin-2-one XI) >, 3-rhodanine XII), 3-imidazolid-2-one XIII), 1-hydantoin l-imidazolidine-2-thione 4-1,2,4-triazole (ZF/) , 1-... 

FIGURE 1 Heterocyclic structures incorporating CO2 and related motifs. (A) l,3-dioxolan-2-ones, (B) l,3-dioxan-2-ones, (C) oxazolidin-2-ones, (D) l,3-oxazinan-2-ones, (E) 1,3,2-dioxathiolane 2-oxides, (F) l,3-oxathiolane-2-thiones. 

With acetic anhydride or dicyclohexylcarbodi-imide, 5-hydroxy-thiazolidine-2-thiones give 2-keto-isothiocyanates R C(0)CR R NCS, which are useful starting materials for the synthesis of imidazolines, oxazolidines, and other heterocyclic systems. ... 

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