Functionally Substituted Compounds

Functionally Substituted Compounds.—Regioselective ortho lithiation of halo-pyridines by LiNPr 2 at — 78°C in THF was reported, i.e., 3-Li-4-X-py (12), 3-X-4-Li-py, and 2-X-3-Li-py from 4-X-py, 3-X-py, and 2-X-py, respectively the thermal stability of (12) was in the order X=F Cl Br I. The compound 2-Li-3-Cl-bicyclo[2.2.1]hept-2-ene (13) obtained from 2-chloro-bicyclo[2.2.1]-hept-2-ene and Bu Li in THF, is stable at 25 °C for 12 h, the bromo analogue of (13) is less stable. Many of the decomposition products of a-BrCeH4Li, 

The compound (Et0)2P(0)CHC0aMe, M+ (18, M=Li or K) exists in THF as chelates and aggregates in Me2SO, (18, M=Li) remains chelated, while both free ions and the chelate exist for (18, M=K). 

The compound 2-Li-2-Me-l,3-dithiane.TMED, (19), crystallizes as centro-symmetric dimers. The lithium bridging leads to a central ring in which Li is 

Seebach, H. Siegel, J. Gabriel and R. Hassig, Helv. Chim. Acta, 1980, 63, 2046. 

Schmidbaur, U. Deschler, B. Zimmer-Gasser, D. Neugebauer, and U. Schubert, Chem. Ber., 1980, 113, 902. 

An improved route to iodomethylzinc iodide has made the iodometh-yltin compounds, R3SnCH2l, more accessible (280). Bimetallic compounds of the types MejSnCBrjMgCl (281), MejSnCClBrLi (282), and MesSnCHIZnI (280, 283), have been prepared in solution at low temperature, and thence, the ditin compounds (MeaSnljCClBr, (MegSnljCBri, (MejSnlaCHI (284). 

These compounds can then be used as a source of a tin-substituted carbene, e.g. (284), 

The iodomethyltin compounds react with amines to give aminometh-yltin compounds, RsSnCHjNRj, and with phosphines to give the phos-phonium ions, MeaSnCHjP Rs, and tris(tributylstannylmethyl)amine has been prepared from (tributyltin)lithium and tris(phenylthio-methyDamine (285). 

The classic route to halogenomethyltin compounds is the methylena-tion of tin halides with diazomethane, and this reaction has been used as the basis for the preparation of a series of thiomethyltin compounds (286). 

Trialkyltin radicals are important intermediates in the reduction of alkyl halides, and in the hydrostannation of alkenes (1, 287). 

---

In all the aprotic solvents (with no proton donor admixtures), the superoxide ion generally cannot act as an oxidant, taking into account a wide range of functionally substituted compounds. For example, in dry pyridine, 07 does not oxidize 1,2-dimethoxybenzene (Sawyer Gibian 1979). This ion, however, reacts with 1,2-dihydroxybenzene. For the OH form, the first step consists of proton transfer from the hydroxyl group to the superoxide ion. Next, reactions proceed with the participation of HOO. The latter is formed according to the disproportionation of Scheme 1-70. 

A similar method was developed for the synthesis of di- and trisubstituted tetrazolium salts through the quaterni-zation of 1- and 2-monosubstituted tetrazoles, including functionally substituted compounds, with diacetone alcohol <1999CHE1078> and tert-butanol <2001CHE949> in perchloric acid, and 2,5-dimethyl-2,5-hexandiol in sulfuric and perchloric acids <2000CHE326>. In the latter study <2000CHE326>, this method was used for a selective synthesis of binuclear N-substituted tetrazoles and tetrazolium salts. 

Trichlorogermane reactions with olefins and acetylenes, including functionally substituted compounds, are one of the basic methods of obtaining organogermanium derivatives. Trichlorogermane adds easily in the absence of any catalyst to olefinic and acetylenic... 

Electrophilic substitution reactions of substituted 2,1-benziso-thiazoles have already been discussed. The only other functionally substituted compound so far studied in any detail is the 3-amino derivative (87). This compound is readily diazotized and the dia-zonium salt formed (88) couples with tertiary aromatic amines yielding azo dyes.117,119-121 The salt (88) also undergoes the usual Sandmeyer reactions, and other 3-substituted derivatives, such as the cyano compound (89) may be prepared.111 Acylation of the amine (87) yields diacyl derivatives which appear to possess the 3-acylimino structure (90).111... 

The a-iodoalkyltin compounds described above react readily with a variety of nucleophiles (alcohols, phenols, thiols, amides etc.) to give further types of a-functionally-substituted compounds R 3SnCHRX (Scheme 6-1).11 26 These will then react with butyl-lithium to give the reagents LiCHRX (Section 22.1) which will react in turn with carbon electrophiles to extend the carbon chain, and this methodology has been exploited extensively in organic synthesis. 

Functionally substituted compounds bearing 192c were prepared from reactions of the corresponding substituted Cp Na, -Li, or -T1 reagents with [IrCl(CO)2(py)]. Ring-substituted compounds synthesized by this route include chloro, benzyl, pentabenzyl, acetyl, carbomethoxy. Me, benzoyl, trimethylsilyl, cyano, dimethylamino, tetraphenyl, dimethylaminoethyl, (tetramethyl)dimethylaminoethyl, methoxyethyl, and pentamethyl. The symmetrical and asymmetrical CO stretching frequencies as well as the C NMR chemical shifts of the carbonyl substituents were correlated with various Hammett substituent parameters. ... 

The group H2C=CHCH2 — IS known as allyT which IS both a common name and a permissible lUPAC name It is most often encountered m functionally substituted deriv atives and compounds containing this group are much better known by their functional class lUPAC names than by their substitutive ones... 

Catalysis. Platinum-catalyzed hydrosilation is used for cross-linking siUcone polymers and for the preparation of functionally substituted silane monomers (250). The most widely used catalyst is chloroplatinic acid (Spier s catalyst), H2PtCl3. Other compounds that catalyze the reaction include Pt(Il)... 

Since the discovery of the first perfluoroalkyllithium and -magnesium compounds, their reactions with various carbonyl compounds [68] have been actively studied. These reactions could lead to functionally substituted fluoro compounds, as shown in equation 36... 

Pentafluorobenzyl bromide has been used in the derivatization of mercaptans [55] and phenols [36], m the analysis of prostaglandins [37], and in quantitative GC-MS [5S] 1,3 Dichlorotetrafluoroacetone is used for the derivatization of amino acids to the corresponding cyclic oxazolidinones and allows the rapid analysis of all 20 protein ammo acids [d] Pentafluorophenyldialkylchlorosilane derivatives have facilitated the gas chromatographic analysis of a wide range of functionally substituted organic compounds, including steroids, alcohols, phenols, amines, carboxylic acids, and chlorohydrms [4]... 

Synthetically, vicinal functionally substituted aryl- and hetarylacetylenes are promising intermediates for preparing different condensed heterocyclic compounds, taking into account the fact that these polyfunctional groups can be selectively involved in cyclization processes. 

The hydrostannation reaction can proceed either by a free-radical mechanism, or, with polar-substituted alkenes or alkynes, by a polar mechanism, respectively resulting in anti-Markownikoff or Markow-nikoff orientation. Both t3rpes of reaction are particularly suitable for preparing functionally substituted, organotin compounds. 

With functionally substituted, alkyltin compounds, the functional substituent may become involved in the cleavage process, resulting in an intramolecular reaction, e.g.. 

As explained earfier step polymerisations generally occur by condensation reactions between functionally substituted monomers. In order to obtain high molar mass products bifuncfional reactants are used monofunctional compounds are used to control the reaction while trifunctional species may be included in order to give branched or crosslinked polymers. A number of types of reaction may be involved, as described briefly in the following paragraphs. 

Chiral phosphoryl and sulfinyl groups are known as efficient auxiliaries in asymmetric synthesis. As reported below, their asymmetric induction in the a-posi-tion has been used to prepare chiral non-racemic organophosphorus compounds a-substituted by a sulfur function. Such compounds can also be obtained from their a-hydroxy analogues by OH-4 SR stereoselective transformation. 

---