V Heterocycles

The five-membered pentavalent iodine heterocycles represent a particularly important class of hypervalent iodine compounds. Cyclic iodine(V) compounds, such as IBX 212 and DMP 213, have found broad practical application as mild and selective reagents for the oxidation of alcohols and some other useful oxidative transformations. Several comprehensive reviews of the chemistry and synthetic applications of IBX and DMP have been published (2011JOC1185, 2006ARK26, 2010T7659, 2011AGE1524, 2001ACE2812). 

1 Five-Membered lodine(V) Heterocycles with an Oxygen Atom in the Ring 

In the solid-state, IBX has a three-dimensional polymeric structure formed by strong intermolecular secondary interactions and hydrogen bonding. 

An X-ray diffraction study of IBX samples, prepared by the oxidation of 2-iodobenzoic acid with potassium bromate in sulfuric acid, revealed the presence of both powder and macrocrystalline forms of IBX (1997CSC589). It was also reported that the powder form of IBX is more reactive than the macrocrystalline form in the reaction with acetic anhydride and thus is more useful as the precursor to DMP (see stmcture 213). The macrocrystalline IBX can be converted to the more reactive powder form by treatment with aqueous sodium hydroxide and then with hydrochloric acid (1997CSC589). 

IBX is a potentially explosive compound, and even the bromate-Jree samples of IBX are not safe. Santagostino and coworkers reported that pure IBX typically explodes at 233 °C (1999JOC4537). The explosibility tests of analytically pure IBX samples (over 99% purity) confirmed the earlier observations by Plumb and Harper that IBX is explosive under impact or heating above 200 °C. 

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V-Heterocyclic carbenes (NHCs) have become an incontrovertible class of mole-cnles for transition-metal- (TM) and organo-catalysis. Inception of the field dates back almost a centnry ago when Tschngajeff (Chugaev) and co-workers reacted... 

V-Heterocyclic Carbene Complexes in Arylation Reactions other than Cross-couplings... 

V-HETEROCYCLIC CARBENES IN TRANSITION METAL CATALYSIS AND ORGANOCATALYSIS... 

Dr. S. T. Reid has contributed the first of two sections on photochemistry of heterocycles, the present one dealing with that of /V-heterocycles. This updates part of his own earlier review The Photochemistry of Heterocycles published in 1970 in Volume 11. A further contribution, which will extend the updating to O- and 5-heterocycles, should be published shortly. Dr. A. B. Hornfeldt s review, entitled Selenophenes, also deals with a subject that was previously reviewed in Volume 12 of this series by N. N. Magdesieva. 

The synthesis of (V-heterocyclic isothiocyanates has been a difficult challenge due to their propensity to oligomerize by autocatalysis. In an attempt to alleviate this issue, silver thiocyanate was used in a novel synthesis of 4-quinolyl isothiocyantes <06TL2161>. Reaction of 4-chloroquinoline with silver thiocyanate in refluxing anhydrous toluene for 12 h results in the desired product in quantitative yields and excellent purity. 

Multidentate V-heterocyclic ligands, thorium and, 24 767 Multidimensional gas chromatography, 4 617-618 6 433-434 Multidrug resistant bacteria, 18 252 Multi-effect distillation (ME), 26 65—67 Multi-effect vapor-compression submerged-tube desalination plant, 26 70 Multielevation piperacks, 19 515 Multifeed fractionation, 10 616 Multifilamentary superconductor, 23 846 Multifilament sutures, 24 218 threads for, 24 207 Multifilament yarns, 11 177-178 Multifile patent searches, 18 244 Multifunctional aliphatic epoxies, 10 376 Multifunctional coatings, 1 714-716 Multifunctional epoxy resins, 10 367-373, 418, 454... 

Acetamides of type (83) derived from various /V-heterocycles have been prepared and investigated for antileukaemic activity in the German Democratic Republic. Within this series, the pyridazine derivative (84) was found to be the only active compound inhibiting the growth of L-1210 mouse cells in vitro (IDS0 10 4 mol/I) [297],... 

The synthesis of 2-thioxo-1,3-0,/V-heterocycles connected to glycopyran and glycofuran scaffolds involves the formation of fused, anchored or spiro structures. The synthesis of such compounds is an attractive challenge from a chemical point of view but also from the growing interest concerning their biological properties. 

T. Deligeorgiev, A. Vasilev and K.-H. Drexhage, Synthesis of novel intermediates for cyanine by the quaternization of V-heterocycles with acrylamide and N-alkyl acrylamides. Dyes Pigm., 67 (2005) 21-26. 

Scheme 2.11 Versatile V-heterocyclic building blocks derivable from fructose in one-pot...

Loss of formaldehyde is not only among the low critical energy processes of oxi-rane and oxetane molecular ions, but also of larger cyclic ethers such as tetrahy-drofurane and tetrahydropyran. [219] Again, imine loss from/V-heterocycles [220] behaves analogously. The mass spectra of tetrahydrofuran, pyrrolidine, tetrahydropyran, and piperidine are compared below (Fig. 6.52). The strong [M-H] peaks in all of those four spectra are due to a-cleavage. 

Nolan SP (2006) V-Heterocyclic carbenes in synthesis. Wiley, New York... 

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