Dioxolane-4-ones

Perfluoroepoxides have also been prepared by anodic oxidation of fluoroalkenes (39), the low temperature oxidation of fluoroalkenes with potassium permanganate (40), by addition of difluorocarbene to perfluoroacetyl fluoride (41) or hexafluoroacetone (42), epoxidation of fluoroalkenes with oxygen difluoride (43) or peracids (44), the photolysis of substituted l,3-dioxolan-4-ones (45), and the thermal rearrangement of perfluorodioxoles (46). 

Miscellaneous OC-Substituted Peroxides. 3-Aryl-3-(/ i alkylperoxy)-phthaHdes (12) are prepared from the corresponding 3-chlorophthaHdes and alkyl hydroperoxide (156). 2-Methyl-2-(/ f2 -alkylperoxy)-l,3-benzodioxan-4-ones (13) are obtained from 0-acetylsaHcyloyl chloride and alkyl hydroperoxides (157). Trisubstituted 2-(/ f2 -alkylperoxy)-l,3-dioxolan-4-ones (14) are synthesized from stericaHy favored a-acyloxy acid chlorides and alkyl hydroperoxides (158). 

The 5-substituted 1,3-dioxolan-4-one 23 is readily deprotonated at the 5 position and can be alkylated with a variety of alkyl halides. The resulting products 24 decompose upon flash vacuum pyrolysis (FVP) at 600°C with loss of acetone... 

Chemical Name 5,5-diphenyl-2-[2-(1-piperidinyl)ethyl]-1,3-dioxolan-4-one hydrochloride Common Nama —... 

S,5R)-2- cr -butyl-5-[(3,)-i-hydroxy-i-phenyletltyl -5-methyl-/ J-dioxolan-4-one yield 81 %... 

Reaction of ketones such as 1-menthone 398 with silylated glycolic acid 417 in the presence of catalytic amounts of TMSOTf 20 provides an lil-mixture of the l,3-dioxolan-4-ones 418 and 419 [35, 36]. Likewise, other aldehydes and ketones [37, 38] and pivaldehyde [39] react with substituted silylated glycohc adds 420 a, b and yS-hydroxy acids 420c to give, e.g., 421 a, b and 421c as mixtures [37-40]. Reaction of pivaldehyde with the persilylated hydroxy acid 420 d and TMSOTf 20 to... 

A patent procedure for formation of compounds 19 from simple tartaric acid derivatives has appeared <06USP047129> and various new routes to chiral dioxolanones include synthesis of dioxolan-2-ones either by transition metal-mediated asymmetric synthesis <06T1864> or enzyme-mediated kinetic resolution <06H(68)1329> and a new synthesis of the chiral dioxolan-4-ones 21 from lactic or mandelic acid involving initial formation of intermediates 20 with trimethyl orthoformate in cyclohexane followed by reaction with pivalaldehyde <06S3915>. 

Under analogous conditions, carbonylation of chloral affords cis or trans 2,5-bis(trichloromethyl)-l,3-dioxolan-4-ones. The stereochemical outcome of the reactions can be controlled by the concentration of the employed sulfuric acid (90-99%) and the reaction time. The cis isomer is predominantly formed under more acidic conditions after 10 min (cis/trans 95/5 48% yield), whereas complete isomerization to the trans isomer (cisltrans 0/100 65% yield) takes place at lower acidity (90%) and prolonged reaction time (7 h) [63]. 

Scheme 6.116 Adducts of the 117-catalyzed Michael reaction between 5-aryl-l, 3-dioxolan-4-ones and various trans-P-nitroalkenes.

I.I.I.3.2.2.3. Lactones with an Additional Heteroatom (O, N, S) in the Ring l,3-Dioxolan-4-ones and l,3-Oxathiolan-4-ones... 

The enolates of l,3-dioxolan-4-ones 1 and l,3-oxathiolan-4-ones2, which are y-lactones substituted with a heteroatom, can be prepared using normal conditions (LDA, THF) and subsequently alkylated. If one takes, e.g.. a nonracemic a-hydroxy acid such as lactic acid 3, then on formation of the heterocycles 1 (R1 = CH3 R2 = alkyl) chirality is transferred from the a-po-sition (C-5) in the starting acid to C-2 in 1, forming (2R,5R)-4 and (2S,5R)-5. If 4 and 5 are easily separable or, even better, if one of them is formed diastereoselectively from 3 then 4 and/or 5 can be transformed to the respective enolates 6 and 7 and alkylated with R X. 

In the case of lactic acid and trimethylacetaldehyde the crude product is a ca. 4 1 mixture of the cis- and the trans-isomers, 4 and 5 (R = /-Bu). respectively75,77 from which pure 4 can be isolated with d.r. 98 2 after one recrystallization at — 78 °C11. Similarly, with 2-/er/-butyl-5-phenyl-1,3-dioxolan-4-one (1, Rl = C6H5 Rz = f-Bu) the crude product is already formed with a d.r. >99 1 75 77 in favor of the m-isomer, giving the pure cw-compound after recrystallization77,79. 

Using the same principle as that described for l,3-dioxolan-4-ones, it is possible to a-alkylate 2-amino acids without racemization76,78. An A. O-acetal is formed from an (7 )-amino acid 1, e.g., with trimethylacetaldehyde (R2 = -Bu) the l,3-oxazolidin-5-ones 2 and 3 are furnished with a defined diastereoselectivity, which is the first stage in the process of self-reproduction of chirality 82. Formation of the enolate 4 from 2 and attack of an electrophile in the second step gives the product 6 with retention of configuration in the a-position, and 7 with inversion of configuration, again with a defined diastereoselectivity. Hydrolysis yields the a-alkylated amino acids 10 and 11. 

For the preparation of 5-alkyl-2-/err-butyl-l,3-dioxolan-4-ones from the bis(trimethylsilyl) derivatives of the /-hydroxy acid and the carbonyl compound catalyzed by trimcthylsilyl tri-flate see also ... 

Observations Six 5-methylene-2-phenyl-l,3-dioxolan-4-one derivatives were prepared... 

TABLE 1. Copoly merization Scoping Reactions Using the Radical Ring-Opening Polymerization Monomer, 5-Methylene-2-phenyl-l,3-dioxolan-4-one, with Methyl Methacrylate... 

The preparation of the radical ring-opening polymerization monomer, 5-methylene-2-phenyl-l,3-dioxolan-4-one, (I), is illustrated in Eq. (1). 

---