1.2- Dithiole-3-oncs

Converting furfuraldehyde into its 1,3-dithian-2-y] derivative by reacting it with propane-1,3-dithiol could also be the basis of a route to furoin. Once deprotonated. this forms an acyl anion equivalent that could be reacted with a second equivalent of the aldehyde and then protonated and deprotected to yield furoin ... 

The 8 + 2-cycloaddition of 2H- eye I o li epta[6] fu ran - 2-onc (155) with acyclic 1,3-dienes provides a facile route to bicyclo[5.3.0] ring systems (156) (Scheme 61).291 2H-Benzo[b]thiete in the o-quinoid form undergoes 8 + 2-cycloaddition with 1,3-dithiolane-2-thione, l,3-dithiole-2-thiones, and adamantanethione to produce 4//-1,3-benzodithianes.292... 

Using the same reactor, a premixed solution of aldehyde or ketone and dithiol (1.0 M, 1 1) in anhydrous MeCN was passed through the Amberlyst-15 126 containing packed bed. The reaction products were again collected in MeCN and analyzed every 10 min by GC-MS. Once optimized, the reactions were conducted for 1 h, to produce the required quantity of each 1,3-dithiane or 1,3-dithiolane, the reaction products were then concentrated in vacuo and analyzed by 1H NMR spectroscopy (Tables 16 and 17) (Wiles et al., 2007b). 

Prepare a mixture of 1,8-dichloro-3,6-dioxaoctane and 3,6-dioxaoctan-1,8-dithiol (23.0 g, 0.125 mol) in a pressure-equalising addition funnel (100 mL) and add the mixture slowly over a period of 2.5 h to the vigorously stirred boiling ethanol solution. Once the addition is complete, heat and stir the mixture for 48 h under nitrogen. 

Another celebrated example of the template effect is the synthesis of crown ethers by Pedersen [11], but it was Busch who first intentionally used templates in synthesis and who first articulated the concept of the template effect in the 1960s [12]. Busch used the reaction of a nickel(Il) dithiolate complex 7 with l,2-bis(bromomethyl)benzene 8 to illustrate his ideas (Scheme 1-3) [13]. Once one end of the l,2-bis(bromomethyl)ben-zene has reacted with the nickel complex, the nickel template induces the reactive ends of the intermediate 9 to come into close proximity and favors cyclization. The metal template allows the synthesis of a metallated macrocycle 10 the free ligand cannot be prepared by the reaction of l,2-bis(bromomethyl)benzene with the unbound thiol (in the absence of a template other cyclic and acyclic products are formed). 

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