Hypervalent heterocyclic compounds

Isothiazolo[5,l-e]isothiazoles [6a-Thia-l,6-diazapentalenes].—Full details have now been provided of a synthesis of compounds of this novel class of hypervalent heterocyclic compounds, which are structurally analogous to 6a-thiathiophthens (see Vol. 2, p. 585), from 6-methyl-l,6a-dithia-6-azapentalenes (81) by successive alkylation and reaction with methylamine. ... 

Synthesis of heterocyclic compounds using hypervalent iodine reagents 98AHC(69)1. 

Diaryliodonium salts, with few exceptions, are stable compounds towards heat, oxygen and humidity they are mildly light-sensitive and should be stored in the dark, without refrigeration. Generally, their reactivity is less pronounced than that of other hypervalent iodine compounds. Indeed, in several of their reactions relatively drastic conditions may be necessary, especially for the least reactive heterocyclic iodonium salts. The search for optimum conditions is often desirable even for well-established reactions, by applying new findings concerning the use of specific... 

The Synthesis of Heterocyclic Compounds with Hypervalent Organoiodine Reagents... 

Applications to the synthesis of heterocyclic compounds of hypervalent organoiodine reagents are covered by Gerald Koser (University of Akron, Ohio) who is well known for his own book in the field. The present review provides continuity with the earlier comprehensive treatment of the subject by Moriarty and Prakmash in Volume 69 of Advances in Heterocyclic Chemistry, which covered the field up through 1996. 

H. H. Karsch, R. Richter, E. Witt, "Novel Sila-Phospha-Heterocycles and Hypervalent Silicon Compounds with Phosphorus Donors", in Organosilicon Chemistry III From Molecules to Materials (Eds. N. Auner, J Weis), VCH, Weinheim, 1997, p. 460. 

Novel Sila-Phospha-Heterocycles and Hypervalent Silicon Compounds with Phosphorus Donors... 

Syntheses of heterocyclic compounds with hypervalent organoiodine reagents 04AHC(86)225. 

The chemistry of 7r-hypervalent heterocyclic systems is one of the important fields in that of hypervalent compounds. A number of 7r-electron systems containing a 10—S—3 framework have been prepared, and their structures and reactivities have been investigated [79]. In general, all atoms bonded to central atom in 7r-sulfuranes such as trithiapentalene are in the same plane. The equatorial bond has the characterization of a double bonding system and the two apical bonds are a 3-center 4-electron bond. As the sp2 type carbon atom or heteroatom having a lone electron pair is located in the two five-membered ring systems, a 1271 conjugated system is constructed and plays an important part in the stability of 7r-sulfurane. 

For reactions of hypervalent iodine reagents in the synthesis of heterocyclic compounds, see Prakash, O. Singh, S.P. 

Koser, G. F., The Synthesis of Heterocyclic Compounds with Hypervalent Organoiodine Reagents, 86, 225. 

Hypervalent 10-electron structures are commonly observed in heterocyclic compounds of Group 13 metals (2001ACR201). Representative examples of such compounds can be illustrated by the alumoxane 17 (2013OM6647) and the complexes of aluminum with nitrogen l ands 18—20 (2009JCS(D) 8631) shown in Figure 5. 

Hypervalent 10-electron structures are commonly observed in the compounds of germanium, tin, and lead (2002MI3). Representative examples of such heterocyclic compounds are illustrated by germanium cyclic oxa-mide complexes 27 (2009JCS(D)4695) and cyclic pentaorganostannate 28 (2007JA10974) shovm in Figure 6... 

Numerous stmctural types of hypervalent phosphorus compounds are known (1999MI1). Representative examples of stable hypervalent phos-phoms heterocycles include lO-P-3 compounds 29 (1994CR1215), anionic lO-P-4 species 30 (1983CB3301), pentacovalent lO-P-5 compounds 31... 

In a more recent work, Kornev and coworkers reported the preparation and structural studies of a series of phenylpyrazole-based hypervalent phosphorus compounds 34 and 35 (Figure 8), which represent another example of low-coordinate hypervalent phosphorus heterocycles (2015EJIC2057). According to X-ray structural data, the phosphorus atom in molecule 34 has overall trigonal bipyramidal geometry with chlorine atoms at the apical position, while the N- and C-substituents and the lone electronic pair are occupying the equatorial positions with P—N and P—C bond distances of 1.771 and 1.831 A, respectively. 

Hypervalent heterocyclic structures are typical of arsenic, antimony, and bismuth. The chemistry of these compounds has been overviewed by K.-Y. Akiba (2011HC207) and several specific examples are illustrated by structures 36—44 (Figure 9). 

---