Cyclic dicarbonate

Lipase CA catalyzed the polymerization of cyclic dicarbonates, cyclobis (hexamethylene carbonate) and cyclobis(diethylene glycol carbonate) to give the corresponding polycarbonates [105]. The enzymatic copolymerization of cyclobis(diethylene glycol carbonate) with DDL produced a random ester-carbonate copolymer. As to enzymatic synthesis of polycarbonates, reported were polycondensations of 1,3-propanediol divinyl dicarbonate with 1,3-propanediol [110], and of diphenyl carbonate with bisphenol-A [111]. 

Cyclic dicarbonates, cyclobis(hexamethylene carbonate) and cyclobis(diethylene glycol carbonate), were polymerized by lipase CA.188 The random ester-carbonate copolymers were enzymatically obtained from DDL-cyclobis(diethylene glycol carbonate) and lactides-TMC.189... 

A novel one-pot synthesis of sulfur-containing polymers including poly(monosulfide)s (polythioethers), poly(disulfide)s, polythioesters, and poly-thiourethanes from a five-membered cyclic dithiocarbonate (5-phenoxjunethyl-l,3-oxathiolane-2-thione) and diamines has been examined. Polythioethers with Mn = 2600-17,700 were obtained by condensation of in situ forming dithiol with o ,a -dibromo-p-xylene [623-24-5] (25). A synthesis by using a bifimctional five-membered cyclic dicarbonate and benzylamine [100-46-9] has also been reported (26). 

Cyclic dicarbonates, cyclo /s(hexamethylene carbonate) and cyclo /s(diethylene glycol carbonate) were polymerised by lipase from C. antarctica and P. fluorescens [62]. CALB was used for the ROP of cyclo /s(decamethylene carbonate) (DMC2) giving a polymer with a MW of 5.4 x 10 and 99% yield, and an ultralow enzyme/substrate weight ratio of 1/200. Compared with six-membered trimethylene carbonate, a much lower reaction activity of large-sized DMC2 vvas observed, the opposite of the enzymatic polymerisation of lactones with different ring sizes [63]. 

Chemical catalysts such as stannous octanoate, methylaluminoxane and aluminium isopropoxide have been used for the copolymerisation of TMC and 15-pentadecanolide (PDL), and the results showed that TMC had much greater reactivity than PDL. In contrast, for the Novozyme-435-catalysed copolymerisation, PDL had a greater reactivity than TMC. Cyclic dicarbonates, cyclo/ /s(hexamethylene carbonate) and cyclo/ 2s(diethylene glycol carbonate) have been copolymerised with e-CL and 12-dodecanolide (DDL) using CAL in toluene at 60 °C for 48 h (Scheme 12.12) [62]. 

Monomers used for ROP are cyclic carbonates or cyclic dicarbonates of different ring sizes derived from a,(0-diols (Scheme 12.6). 

Polycarbonates with diethylene or triethylene glycol moieties were obtained by ROP of the corresponding cyclic dicarbonates 37 and 38. These polymers are crystalline and hydrophilic, and suitable for the preparation of amphiphilic copolymers [78]. 

Cyclic ketones are suitable starting material for the preparation of corresponding oximes and dicarbonic acids, which are key intermediates for the production of various types of nylons. Recently, BASF announced [176] the development of a new process for cyclododecanone production via the ketonization of cyclododecene (entry 4, Table 7.9), for which commercialization is expected in 2009. 

The stereochemical factors influencing the formation of cyclic carbonates have not been fully elucidated, and the number of derivatives whose structures have been unequivocally proved is quite small. In fact, the structures of the known cyclic carbonate derivatives of pyranosides have all been allocated on the basis of analogies with corresponding 0-isopropylidene acetals. This is particularly unfortunate where the possibility of both five-and six-membered carbonate rings exists, as in the case of 1,2 3,4- and 1,2 4,6-dicarbonate esters of D-galactopyranose (VII VIII). A five-mem-... 

It is also worthwhile to note that the relatively slow catalytic hydrogenolysis of A/ -Z-protected peptide derivatives pemnits some interesting chemical transformations to be performed in situ. For example, direct conversion of Z protection to Boc protection is possible when the hydrogenation is conducted in the presence of di-tert-butyl dicarbonate under neutral conditions.h Alternatively, the same transformation is achieved by the use of triethylsilane and di-tert-butyl dicarbonate in ethanol with catalytic amounts of palladium(II) acetate.h 1 More efficiently this one-pot transformation is achieved by catalytic transfer hydrogenation in the presence of di-terf-butyl dicarbonate (cf. Section 2.1.1.1.3.1.1.6).h l Similarly, peptide cyclization reactions have been performed in situ over Pd/C and the high yields of cyclic monomers are attributed to the high dilution effect as well as to catalysis of the charcoal surface.h l... 

By electrochemical oxidation in alcoholic solution, e.g. in the presence of alkoxides, of aldehyde acetals or 1,3-dioxolanes derived from aldehydes orthoesters, e.g. (400 equation 185), can be obtained. " Orthobenzoates (401 equation 186) are accessible by electrolysis of substituted toluenes in the presence of triarylamines in solvents such as methanol/meAylene chloride. Decarboxylation and subsequent electrochemical oxidation of the dicarbonic acid (402 equation 187) in methanol affords cyclic orthoesters (403). ... 

N-(l-Alkoxyalkyl)-aniides or -carbamates (2 X = OR), most frequently used as stable precursors for A -acyliminium ions, are usually prepared by one of the following routes (equations 7-13). For five- or six-membered cyclic cases a simple acid-catalyzed solvolysis of the hydroxy compound provides the alk-oxy derivative (equation 7). A silicon-assisted approach involves the TMSOTf-catalyzed reaction of bis(trimethylsilyl)formamide with aldehydes (equation 8). /V-(l-Trimethylsilyloxyalkyl)formamides are thus formed in good yields, which on TMSOTf-catalyzed solvolysis lead to the /V-( 1-alkoxyalkyl)form-amides. A third method is based on the NaBH4 reduction of imidates (equation 9), and has proved useful for a total synthesis of the insect poison pederine. Addition of reactive acid derivatives to imines constitutes another method (equations 10 and 11). Acylation with acid chlorides followed by treatment with ethanol in the presence of base leads to N-(l-alkoxyalkyl)amides. A one-step protocol using diethyl dicarbonate provides the corresponding carbamates. 2... 

Organoazides. Alkyl azides are obtain by using the MejSiNj-Bu NF reagent systen corresponding bromo derivatives in a reactioa A cyclic allylic azide is required for a synd is obtainable from a Pd-catalyzed reaction of dicarbonate in the presence of a chiral ligand... 

Studied computationally. B3LYP/6-31G calculations indicate that this process has a barrier of 68.8 kJ mol and a reaction energy of 83.1 kJ mol . Thus this acyclic dimer seems to be less fragile and less energetic than the cyclic dimer (barrier 40.7, reaction energy 182kJmol ). Esters of the dimeric 3-CO2, dicarbonic acid or pyrocarbonic acid, are known and are stable (analogonsly to the fact that esters of... 

The unsaturated double bonds in limonene can be epoxidized (11). Carbon dioxide and limonene oxide can be used to get a cyclic limonene dicarbonate. The reaction is shown in Figure 6.4. This compound is useful to produce linear polycarbonates, or poly(ur-ethane)s (PU)s. 

Scheme 12.92 Meso desymmetrization of a cyclic allylic dicarbonate [195].

Other resnlts obtained by Tsnji s group up to 1987 using allyl carbonates are carbony-lations to afford /3,y-nnsatnrated esters " (Scheme 3) (see Sect. VI.3), cycloadditions of trimethylenemethane palladium complex to afford methylenecyclopentanes (Scheme 3), and cycloadditions of zwitterions to afford substituted vinylcyclopentanes (Scheme 4) (see Sect. V.2.5.2). 2-Butene-1,4-diol dicarbonates afford a variety of cyclic strnctnres by reaction with dinncleophiles nnder Pd(0) catalysis (see Sect. I). The first case reported seems to be the formation of the vinylcyclopropane of Scheme 44" ... 

The reaction of the dicarbonate with acidic anilines produces 3-aryl-4-vinyloxazoli-dine-2-ones.f Finally 10-, 15-, and 20-membered rings have been isolated in the reaction of arenesulfonamides with the butene-1,4-diol dicarbonate, and higher rings have been detected by mass spectrometry techniqnes. In these reactions a stable Pd(0) complex of the 15-membered ring is isolated, and cyclic monomeric compounds are always accompanied by polymeric material. 

Several types of cyclic carbonates have been used in Pd(0) chemistry. They wiU be treated separately. Perhaps the most simple case is the cyclic carbonate of 2-methylene-l,3-diol (Scheme 43). Tsuji and co-workers " and Breuilles and Uguen used this compound to activate one alcohol function toward substitution while protecting the other. Note that dicarbonate of the same diol activates both alcohols (Scheme 42). 

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