With dihalides

Other interesting synthetic applications of the ketone-derived enamine alkylation are found in the monomethylation of steroid enamines (249), extension of the benzylation reaction (250) to a ferrocene derivative (251), the use of a-bromoesters (252) and ketones (252) or their vinylogues (25J), in the syntheses of alantolactone (254-256), isoalantolactone (257), and with a bridged bis-enamine (258). The use of bifunctional alkylating agents is also seen in the introduction of an acetylenic substituent in the synthesis of the characteristic fragrant constituent of jasmine (259), the synthesis of macrocyclic ketolactones (260), the use of butyrolactone (261), and the intermolecular or intramolecular double alkylations of enamines with dihalides (262). 

Ethers from alkylation of furfuryl alcohol with dihalides were obtained under solvent PTC + MW conditions with quasi-quantitative yields (Eq. 38) [19]. 

The most widely used dihalide is 1,2-dichloroethane. The use of polyhalides (e.g., 2% 1,2,3-trichloropropane) results in the formation of branched or crosslinked products. Sodium tetrasulfide (Na2S4) is generally used as the polysulfide since it contains scarcely any of the monosulfide which reacts with dihalides to form cyclic by-products with unpleasant odors. 

More recently, the doubly lithiated derivatives of [4.1.1]- and [3.1.1]propellasilanes underwent bridging metathesis at the bicyclobutane ends with dihalides of germanium, tin and transition metal titanium, to give the corresponding highly strained metallacyclic propellanes (equation 7)29. 

The preparation of three-, five- and six-membered rings in modest yield by the elec-trochemically induced coupling of activated olefins with dihalides has been reported (equation 35)98. Use of an aluminum anode was critical for the formation of cyclized product. Application of this technique to the preparation of four-membered rings was unsuccessful. 

Bisquaternary salts of berberine, dihydroberberine, and other alkaloids have been prepared by quaternization with dihalides such as 2,2 -dichlorodiethylamine, sarcolysin, and cyclophosphane.105... 

A wide range of macrocyclic polythioethers are known and have been obtained by elegant synthetic routes (102), yet relatively few of these macrocycles have been by template methods, unless the sodium ion serves to coordinate the sulfur atom in the reactions of disodium salts of thiols with dihalides. Some examples of macrocycles prepared by this route are LXX-LXXII (5), LXXIII and LXXIV (120), and LXXV (15). 

Cycloalkylation of the A iV -disubstituted 1,2-diamines 80 with dihalides 81 produced the diazocines 82 in an optically active form (Equation 12) <2004TA2437, 2005TL3473>. 

The new selenacrown ether A,A -dimethyl-l,ll-diaza-4,8,14,18-tetraselenacycloicosane 32 has been synthesized and characterized <2005MI191>. Xu et al. have reported the first selenacrown and selenazacrown ethers bearing a hydroxy group. In this series, the key step is the preparation of the diselenide intermediate 188 by a reduction with potassium borohydride. It can then be condensed with dihalides or diol ditosylates 191 to give the aza 10-membered... 

An improved method for the preparation of selenacrown ethers has been described by Xu and co-workers. The synthesis of poly-(o-diselenobenzene) was detailed as the key intermediate for the syntheses of o-benzene diselenium type of selenacrown ethers. Under alkaline conditions, 5,6,1 l,12-tetraselena-dibenzo[tf/]cyclooctene 212 was reduced with potassium borohydride to give o-benzenediselenolate anion 213, which condensed with dihalides 215-217 and different 12- and 24-membered selenacrown ethers 218 and 219 were isolated in good yields (Scheme 31) C1995MI1559, 1997JCD1043, 1999JCD1039>. 

Lactones with oligoheteryl units in the macrocyclic ring skeleton can also be prepared in good yields from the reaction of cearan carboxylates with dihalides. Potts [53] obtained the triheteryl lactones 51 with a pyridine (X=CH) and a pyrimidine unit (X=N) in 60% (X=CH) and 55% yield (X=N) by cychzing the cesium salt 49 with the dibromo ojmpound 50 using DMF as solvent. 

Secondary amines an easily converted into formamidines reaction with amidines (equation 24). Deprotonation and addition of electrophiles, including alkyl halides, acyl halides, aldehydes and dise-lenides, permit the introduction of various groups adjacent to the amino center, and therefore can be considered as an oxidation. Alkylation with dihalides gives intermediates which lead to new caibocyclic rings after removal of the formamidine group (equation 2S). ... 

The key step for the conversion of open-chained a,3-unsaturated aldehydes to their corresponding cyclized carbonyl compounds involves the regioselective alkylation of (39) with dihalides. 

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