1,3-Hetero cyclics

Hetero)cyclic hydrocarbons Ln.J T.n.J L beginning of a carbocyclic ring T beginning of a heterocydic ring n number of atoms of the ring system f termination of the ring system... 

Imidazole and its derivatives form an interesting and important class of hetero cyclic aromatic amines Imidazole is approximately 100 times more basic than pyndme... 

Cycloaddition reactions catalysed by transition metal complexes are an important tool in the construction of a wide range of carbo- and hetero-cyclic systems, such as benzene, pyridines, triazoles, etc. [7]. In general, these reactions are extremely atom-efficient and involve the formation of several C-C bonds in a single step. Among the innumerable possible catalytic systems for the cycloaddition reaction the NHC-metal complexes have received special attention [7c]. 

Nakahara, T. Nakajima, T. Nomura, N., and Nekotsuka, S., Microbial desulfurization of sulfur-containing hetero-cyclic compound Patent No. JP10243791. 1998, Sep. 14. 

Microbial desulfurization of sulfur-containing hetero-cyclic compound [156],... 

El-Sayed, M. A. Spin-orbit coupling and the radiationless processes in nitrogen hetero-cyclics. J. Chem. Phys. 38, 2834 (1963). 

The vicarious nucleophilic substimtion of carbo- and hetero-cyclic nitroarene hydrogen by a hydroxyl group, on reaction with silylhydroperoxide anions, has been shown to proceed via nucleophilic addition of ROO followed by base induced elimination of ROH by an ii2-type mechanism the required orientation of the hydroxylation can be controlled by the conditions selected. ... 

During the coverage period of this chapter, reviews have appeared on the following topics reactions of electrophiles with polyfluorinated alkenes, the mechanisms of intramolecular hydroacylation and hydrosilylation, Prins reaction (reviewed and redefined), synthesis of esters of /3-amino acids by Michael addition of amines and metal amides to esters of a,/3-unsaturated carboxylic acids," the 1,4-addition of benzotriazole-stabilized carbanions to Michael acceptors, control of asymmetry in Michael additions via the use of nucleophiles bearing chiral centres, a-unsaturated systems with the chirality at the y-position, and the presence of chiral ligands or other chiral mediators, syntheses of carbo- and hetero-cyclic compounds via Michael addition of enolates and activated phenols, respectively, to o ,jS-unsaturated nitriles, and transition metal catalysis of the Michael addition of 1,3-dicarbonyl compounds. ... 

The cyclizahon of amino alcohols should be an attractive method for the synthesis of N-heterocyclic compounds, mainly because they can be obtained in a single step and without the generation of wasteful byproducts. Carbon-nitrogen bond formation catalyzed by Cp lr complexes has been extended to the synthesis of N-hetero-cyclic compounds by the cyclization of amino alcohols. 

A.Weissberger, ed," Chemistry of Hetero cyclic Compounds , Interscience-Wiley,... 

Another variant of the photochemical reaction between A-hetero-cyclic o-quinones and olefins has been described by Mustafa et al.196 200 Stilbene reacts with CXLIX and with CL to give the photoproducts CLVIII and CLIX, respectively. Similar photoaddition products were obtained by the interaction of phenanthraquinone with a-stilbazole245 and with l,2-di-(4 -pyridyl)ethylene.241 Although the process has been suggested as involving diradicals, it is not clear whether the quinone or the olefin undergoes photoexcitation. 

The synthesis of spirocyclic and fused unusual (3-lactam derivatives has been discussed. The 2-azetidinone skeleton has been extensively used as a template on which to build the carbo(hetero)cyclic structure joined to the four-membered ring, using the chirality and functionalization of the (3-lactam ring as a stereocontrolling element. In many cases the compounds described in this chapter were included because of an interesting synthesis or structure, although limited biological data were found. 

Li and coworkers have previously found that in the presence of an /V-hetero-cyclic carbene catalyst m-4-formyl-(3-lactams underwent the ring expansion reaction to afford succinimide derivatives [242]. More recently, they reported the kinetic resolution version of this transformation attempted with a chiral /V-heterocyclic carbene (Scheme 113), leading to m-4-formyl-(3-lactams with moderate ee of 64% [243]. 

An efficient, practical solid-phase synthesis of a variety of bis-hetero-cyclic compounds was developed starting from resin-bound orthogonally protected lysine (Fig. 10). Tetraamines 36 were synthesized by exhaustive reduction of resin-bound tetraamides 35. Cyclization with different commercially available bifunctional reagents such as cyanogen bromide, thio-carbonyldiimidazole, carbonyldiimidazole, and oxalyldiimidazole yielded the corresponding bis-heterocyclic compounds bis-cyclic guanidines 37,39 bis-cyclic thioureas 38, bis-cyclic ureas 39, and bis-diketopiperazines 40, respectively.40 Reduction of compounds 40 led to bis-piperazines 41. 

Similarly, it is possible to classify the reactions in polycyclic hetero-cyclics. The situation is then complicated by the possibility that the substituent on the electroactive grouping can be attached either to the heterocyclic or to the benzenoid ring. 

Heterocyclic compounds contribute significantly to the overall aroma impression of meat. They include 0-, N-, and S-hetero-cyclic structures. Meat flavor heterocyclics include furans,... 

Photochemistry of (S-Hetero)cyclic Unsaturated Carbonyl Compounds Paul Margaretha... 

The benzothiazolyl group (BT) can play several roles in one, it enables a more or less strongly pronounced complexation that influences the selectivity on the other hard, it can also undergo nucleophilic substitution at the carbon attached to the sulfonyl group, which then becomes a leaving group. Other (hetero)cyclic substituents can assume these roles, and offer somewhat different selectivity ... 

ADF-DFT calculations indicated the presence of a-type orbital interactions mainly generated by the U(/z3) orbital with a minor contribution from the C—H (.v// )-type of orbitals. Incidentally, the same complex reacts with an /V-hetero-cyclic carbene to form the corresponding U(III)-carbene adduct (20). 

The synthesis of five-membered carbo- and hetero-cyclic compounds, including fused rings, has been reported using acetate as a nucleophile in the cyclization of 1,6-enynes under palladium(II) catalysis (Scheme 91). The reaction is initiated by trans-acetoxypalladation of the alkynes and quenched by either trans- or ra-deaceloxypal-ladation in the presence of 2,2/-bipyridine as the ligand.134... 

Effect of Phospholipids on Reaction Volatiles. As would be expected, the inclusion of phospholipids in the reaction mixtures produced many volatiles derived from lipid degradation these included hydrocarbons, alkylfurans, saturated and unsaturated alcohols, aldehydes and ketones. However, two other important observations were made. First, the concentrations of most of the hetero- cyclics, formed by the amino acid + ribose Maillard reaction, were reduced. For most of the major volatiles this reduction was of the order of 40 - 50%, but in the case of thiophenethiol and methyl- furanthiol the reduction was over 65%. This appears to support the findings that in meat and coconut, lipids exert a quenching effect on the amount of heterocyclic compounds formed in Maillard reactions during heat treatment (11,12). Second, and perhaps more important, the addition of phospholipid to the reaction mixtures resulted in the production of large amounts of compounds derived from the interaction of the lipid or its degradation products with Maillard reaction intermediates. 

Cycloalkanes and Saturated Hetero-cyclics The chemical shifts of the CH2 groups in monocyclic alkanes are given in Table 4.7. The striking feature here is the strong shift to the right of cyclopropane, analogous to the shift of its proton absorptions. 

Sometimes the reaction products depend on the deprotonation method used. For example, RajanBabu and coworkers have obtained chiral N-hetero-cyclic biscarbenes of Pd and Ni from a binaphtyl bisimidazolium salt. The in situ deprotonation of the bisimidazolium salt with KOfBu prior to the addition of Pd(OAc)2 gives exclusively the trans isomer, 24, while direct reaction of the salt with the metal complex in hot DMSO (see next section) gives a mixture of the cis-(25) and trans-isomers (Scheme 17) [81]. 

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