N acyclic

Scheme 36 Anodic decarboxylation of N-acyl a-amino acids to a N-acycl iminium intermediates.

C=0)-halogen, 0-(C=0)-halogen, S02-halogen, N=C=0, N=C=S, N-C(=S)-N Acyclic C(=0)-S, acyclic C(=S)-0, acyclic N=C=N Anhydride, aziridine, epoxide, ortho ester, nitroso Quaternary amines, methylene, isonitrile Acetals, thioacetal, N-C-O acetals Nitro group, >1 chlorine atom... 

Acyclic semicarbazones usually exhibit a band at 1675-1645 cm for C=N. Acyclic thiosemicarbazones display a weak band at 1650-1630 cm the thiosemi-carbazones of seven aldoses did not have this band, and were therefore considered to have a cyclic structure (Holker, 1964). 

P-NHj P=N cyclic compounds P=N acyclic compounds Phosphonic add phosphonous acid... 

Sheppard N and De La Cruz C 1996 Vibrational spectra of hydrocarbons adsorbed on metals. Part I. Introductory principles, ethylene, and higher acyclic alkenesAdv. Catal. 41 1-112... 

For example, when an N-methylthioacetamide (96), R, = R — Me, was condensed with chloroacetone, a 2,3,4-trimethylthiazolium chloride was obtained in quantitative yield. The reaction is usually run in aqueous or alcoholic solution at room temperature. At low temperature, with N-phenylthioacetamide (96), Rj = Me, R2 = Ph and chloroacetone, an acyclic intermediate (98) was isolated and characterized (Scheme 43). It was easily converted to 2,4-dimethyl-3-phenylthiazolium chloride (97), R, = Rs = Me, Rj -Ph, by heating (99,102, 145). 

Cyclic diesters are often even better substrates forlipases and esterases than acyclic derivatives. Small-ring monoacetates (28, n — 1-3) are obtained in higher yield and ee than the larger derivatives (for 28, n = 4 is only 50%) (43). Hydrolysis of tetrahydrofuran diester results in monoester (29) of ee > 99% (44). 

It has been found that an acyclic NCCN system in which the N—C groups may be sp,... 

Alkylisothiazolium salts (61) undergo N—S bond cleavage when treated with hydrogen sulfide or thiophenol to form acyclic products (62), but 2-aryl compounds give 1,2-dithioles (63 or 64 Scheme 9) (75SST(3)54l, 77SST(4)339). 

The accessibility of the +4 and +6 oxidation states for sulfur and, to a lesser extent, selenium gives rise to both acyclic and cyclic molecules that have no parallels in N-O chemistry. Thus there is an extensive chemistry of chalcogen diimides RN=E=NR (E = S, Se, Te) (Section 10.4). In the case of Te these unsaturated molecules form dimeric structures reflecting the increasing reluctance for the heavier chalcogens to form multiple bonds to nitrogen. The acyclic molecule N=Sp3,... 

A. Haas, Acyclic and Heterocyclic Te-S-N Compounds A Review of Recent Publications, J. Organomet. Chem., 646, 80 (2002). 

N,N - Bis(trimethylsilyl)sulfur(rV) diimide Me3SiN=S=NSiMc3 is an especially versatile source of the N=S=N functionality in the formation of both acyclic and cyclic S-N compounds. It is conveniently prepared by the reaction of NaN(SiMc3)2 and thionyl chloride (Eq. 2.5). 

Acyclic Se-N chlorides that are potential building blocks (as a source of the SeNSe unit) for cyclic Se-N systems are generated by the reactions of [SeChJiAsEg] or SeCU with (Mc3Si)3N as illustrated by the sequence of transformations that produce the five-membered [Se3N2Cl] cation (Scheme 2.4 and Section 8.4). 

Scheme 2.4 Formation of acyclic and cyclic Se-N cations (i) -3Me3SiCl, -CI2 (ii) GaCl3 (iii) Ph3Sb...

A variety of acyclic and cyclic S-N compounds decompose at moderate temperatures (100-150°C) with the formal loss of a symmetrical NSN fragment, but this molecule has never been detected. The lowest energy isomer, linear NNS, is generated by flash vacuum pyrolysis of 5-phenyl-1,2,3,4-thiatriazole (Eq. 5.1). ... 

NMR and visible spectra have established that a number of S-N anions are present in such solutions.The primary reduction products are polysulfides Sx, which dissociate to polysulfur radical anions, especially the deep blue 83 ion (/Imax 620nm). In a IM solution the major S-N anion detected by NMR spectroscopy is cycZo-[S7N] with smaller amounts of the [SSNSS] ion and a trace of [SSNS]. The formation of the acyclic anion 5.23 from the decomposition of cyclo-Sjl is well established from chemical investigations (Section 5.4.3). The acyclic anions 5.22 and 5.23 have been detected by their characteristic visible and Raman spectra. It has also been suggested that a Raman band at 858 cm and a visible absorption band at 390 nm may be attributed to the [SaN] anion formed by cleavage of a S-S bond in [SSNS]. ° However, this anion cannot be obtained as a stable species when [SsN] is treated with one equivalent of PPhs. 

A different type of behaviour is observed with the chloro Lewis acid BCI3. With this reagent halogen exchange occurs to produce the acyclic cation [N(SC1)2] , as the [BCU] salt, rather than NSCf. " Thiazyl trichloride NSCI3 is predicted to be unstable with respect to NSCl -1-Cl2. ... 

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