Benzo-1,3-dioxan-4-ones

S >Olmethaxytrltyl>2 -d oxythylmldlne-3 -phosphate (3). A sohjllon ot 1 mmol ot 1 (T thymine, DMT-4,4 -dimethoxyti1tyl) in dioxane (8 mL), pyridine (1 mL) and a slight excess ot 2-chloro-5,6-benzo-1,3-dioxaphosphorfn-2-one 2 (1 mi. ot a 1.2S M solution in dioxane) was stirred at 20 C After 5 mki TLC Indicated complete conversion oM Into 3 with zero mobility. Water was added and after work up 3 was isolated in 88% yield. 

In this chapter, the structures and chemistries of 1,3-dioxins, 1,3-oxathiins, and 1,3-dithiins are described, including both their fully saturated forms (1, 7, and 13) as well as their benzo analogs (6, 11, 12, and 17). The formally fully unsaturated monocyclic structures (4, 9, 10, and 16) contain only one endocyclic double bond with further unsaturation being accomodated by exocyclic double bonds (2, 3, 5, 8, 14, and 15), for example, by the introduction of a carbonyl group. Well known and intensively studied are the Meldrum s acid derivatives 18 and 19. In addition, 1,3-dioxane, 1,3-oxathiane, and 1,3-dithiane moieties can be part of spiro structures as well as hi- and tricyclic analogs. And finally, both the structures and chemistries of the corresponding sulfoxides and sulfones are also reported. 

Benzo-l,3-dioxan-4-ones. Phenyl salicylates form cyclic acetals on reaction with HCHO and DABCO in chloroform. The corresponding methyl esters do not react. 

A series of 5-dialkylaminoethyl-benzo-l,5-thiazepin-4-ones (36) has been obtained by reaction of the known benzo-l,5-thiazepin-4-ones (35) with dialkylaminoethyl chlorides and sodium hydride in dioxan or, better, DMSO. The acetoxy-compounds (37) are converted by standard procedures into benzo-l,5-thiazepine derivatives such as (38) and (39). 

A soln. of Ag-nitrate in dioxane-water added to a soln. of 5-bromomethyl-llH-benzo[a]fluoren-ll-one in dioxane, and stored 2 hrs. at room temp. 5-nitrato-methyl-llH-benzo[a]fluoren-ll-one (Y 94%) refluxed 2 hrs. with KOH in dioxane-water llH-benzo[a]fluoren-ll-one-5-carboxaldehyde (Y 91.5%). R. L. Letsinger and J. D. Jamison, Am. Soc. 93, 193 (1961). 

Benzo-l,4-dioxan-3-ones from ketenes and o-qiiinones... 

Oxidative benzo-l,3-dioxan-4-one ring closure 331. GH3O... 

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