1.3- Dioxolium salts

Since the publication of the corresponding chapter in CHEC-II(1996) <1996CHEC-II(3)525>, there have been a large number of developments in the chemistry of 1,3-dioxole systems and these have mainly involved 1,3-benzo-dioxoles 1, 1,3-dioxolanes 2, and the isomeric l,3-dioxolan-2-ones 3 and l,3-dioxolan-4-ones 4. There have been specific reviews on the synthesis of 1,3-dioxolium salts 5 <2002SOS(11)13> and the transformations of the 6,8-dioxabicyclo[3.2.1]octane compounds 6 <2003SL1759>. 

Since the publication of the first edition of Comprehensive Heterocyclic Chemistry (CHEC-I), there has been relatively little new work on the fully conjugated systems, the 1,3-dioxolium salts (1),... 

Lorenz and Maas (1987) found a novel route to alkenediazonium salts in the O-acylation of a-diazo ketones with benzoyltriflate or diphenylacetyl triflate, i. e., with carboxylates with a very weak base, in dichloromethane at -70°C (see Scheme 9-50). They are not stable at higher temperature, but form 1,3-dioxolium salts (see Sect. 9.5). 

When these solutions were slowly heated to room temperature, dediazonia-tion took place and the corresponding 1,3-dioxolium salts 9.125 could be isolated. The lower stability of )ff-(acyloxy)alkenediazonium ions relative to that of jff-alkoxy-ethenediazonium ions is understandable on the basis of the lower electron donating power of the substituents. 

The dioxolium salt derived from 2,2-dichloro-l,3-benzodioxole and BCI3 reacts with isobutylene by nucleophilic attack at C-2 to afford (59) after a second attack on the cation (58) <88CB339>. The... 

The main methods available to prepare 1,3-oxathiolium salts and their mesoionic 4- and 5-olates are of this type and were covered in CHEC-I <84CHEC-I(6)749> but two important new methods have been described. The 2-amino-1,3-oxathiolium salts (208) can be obtained by desulfurization of the phenacyldithiocarbamates (207) with a silver, mercury, or copper salt (Equation (28)) <92JAP04364178>. The l,3-dioxolium-4-olates (210) have been generated from the a-diazo anhydrides... 

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