4,4 -Bis -isopropylidene

Single crystals of 1 1 complex. °1 1 Catalyst obtained by evaporation of CH2CI2. After 3 months in an open air. Ligand (Ff,Ff)-isopropylidene-2,2 -bis(4-phenyl-oxazoline). Anhydrous complex catalyst prepared from NIBr2 and AgSbFg. 

We therefore prepared a new chiral ligand, (l ,J )-isopropylidene-2,2 -bis[4-(o-hy-droxybenzyl)oxazoline)], hereafter designated J ,J -BOX/o-HOBn. To our delight, the copper(II) complex catalyst prepared from J ,J -BOX/o-HOBn ligand and Cu(OTf)2 was quite effective (Scheme 7.45). Especially, the reaction of O-benzylhydroxylamine with l-crotonoyl-3-isopropyl-2-imidazolidinone in dichloromethane (0.15 m) at -40°C in the presence of J ,J -BOX/o-HOBn-Cu(OTf)2 (10 mol%) provided the maximum enantioselectivity of 94% ee. 

Frechet and Lee described the dendronization ofa poly(L-lysine) (12) to the fourth generation via an iterative anhydride coupHng and deketahzation procedure, using an anhydride of isopropylidene-2,2-bis(oxymethyl)-propionic acid (Scheme 37.2)... 

Crystallinity of these hexafluoroisopropylidene-unit-containing poly(ketone)s is low except for poly(sulfide ketone) (13). The water contact angle for the fluorine-containing poly(ketone) films is high, being 98° for poly(ether ketone) (11), from 2,2-bis(4-carboxyphenyl)-l,l, l,3,3,3-hexafluoropropane(15) and 96° for poly(sulfide ketone) (13) from 15, whereas it is 78° for poly(ether ketone) from 2,2-bis(4-carboxy-phenyl)propane (16) and 74° for the poly(sulfide ketone) from 16. This result indicates that the substitution of isopropylidene units of poly-(ketone)s with hexafluoroisopropylidene units has a remarkable effect on the surface properties of poly(ketone) films. 

Another type of film investigated recently has been aromatic cyanate esters prepared from the Ciba-Geigy products AroCy L-10 (l,l-bis(4-cyanatophenyl) ethane) and AroCy B-30 (the prepolymer form of 2,2/-bis(4-cyanatophenyl) isopropylidene, AroCy B-10) [89], The chemical structures of these molecules are shown in 4. Spectral measurements from these aromatic cyanate ester ma-... 

SYNS BISFEROL A (GERMAN) 2,2-BIS-4 -HYDROXYFENYLPROPAN (CZECH) BIS(4-HYDROXYPHENYL) DIMETHYLMETHANE BIS(4-HYDROXYPHENYL)PROPANE 2,2-BIS(p-HYDROXYPHENYL)PROPANE 2,2-BIS(4-HYDROXYPHENYL)PROPANE DIAN p,p -DIHYDROXYDIPHENYLDIMETHYLMETHANE 4,4 -DIHYDROXYDIPHENYLDIMETHYLMETHANE p,p -DIHYDROXYDIPHENYLPROPANE 2,2-(4,4 -DIHYDROXYDIPHENYL)PROPANE 4,4 -DIHYDROXYDIPHENYLPROPANE 4,4 -DIHYDROXYDIPHENYL-2,2-PROPANE 4,4 -DIHYDROXY-2.2-DIPHENYLPROPANE 3-DI-p-HYDROXYPHENYLPROPANE 2,2-DI(4-HYDROXYPHENYL)PROPANE DIMETHYL BIS(p-HYDROXYPHENYL)METHANE DIMETHYLMETHYL-ENE-p,p -DIPHENOL 2,2-DI(4-PHENYLOL)PROPANE p,p -ISOPROPYLIDENE-BISPHENOL 4,4 -ISOPROPYLIDENEBISPHENOL p,p -ISOPROPYLIDENEDIPHENOL NCI-C50635... 

Figure 4 Molecular structure of 4-methoxyphenyl 3,4-0-isopropylidene-2,6-bis-0-(4-methylbenzoyl)-p-D-galactopyranoside (CR). Instead of change in the external magnetic fields, the concentrations of CR were varied for the investigations of cholesteric liquid crystal in magnetic fields.

The ROP reaction of the cyclic oligomers mixture (26) derived from 2,2-bis(4-mercaptophenyl)propane (4,4 -isopropylidene bisthiophenol) was studied in both diphenyl ether solution and melt without adding any catalyst. It was found that... 

Preparation. In this communication, we focus on preparing ultra-thin polymer overlayers on disks starting with the cyanate ester monomer, 2,2 -bis(4-cyanatophenyl)isopropylidene (BCPP), supplied by Ciba Specialty Chemicals. Figure 4 shows the chemical structure of the BCPP monomer and the ring forming cyclotrimerization reaction that occurs when these monomers are heated in the presence of a suitable catalyst. 

Figure 11.21 2,2 -Bis(4-cyanatophenyl) isopropylidene (CE) and Liquid crystalline epoxy resin (LCE).

Isopropylidene or benzylidene 2-hydrazinoselenazole derivatives can be converted to highly colored 2.2 -dioxo-A-3,3 -biselenazol-5,5 -inylidene-bis-hydrazones (Table X-11) by oxidation with ferric chloride and hydrogen peroxide i33). 

TABLE X-11. BIS-ISOPROPYLIDENE OR BENZYLIDENE DERTVATIX S OF 2.2-DIOXO-A-3,3-BISELENAZOL-5.S -rNYLIDENE BIS HYDRA-ZONES (33)... 

Butane, 2,3-0-isopropylidene-2,3-dihydroxy-1,4-bis(diphenylphosphino)-catalyst in homogeneous asymmetric hydrogenation, 6, 781 Butane-1,4-dioic acid, 2,2-di(indolyl)-synthesis, 4, 226 Butanenitrile, 4-hydroxy-dihydropyran synthesis from, 3, 769 Butanoic acid, -y-aryl-y-amino-synthesis, 1, 433 1-Butanol... 

With respect to the nucleophilic addition of organocopper reagents, a sharp contrast between the rigid isopropylidene glyceraldehyde and its open-chained analog, 2,3-bis(benzyloxy)propanal. was observed (compare Tables 15 and 16). With the isopropylidene-protected aldehyde a high syn diastereoselectivity could only be obtained when tetrahydrofuran was used as reaction solvent, and the diastereoselectivity dropped considerably in diethyl ether. In contrast, the latter solvent allows excellent syn selectivities in additions to the dibenzyl-protected glyceraldehyde81. On the other hand, tetrahydrofuran yields better results than diethyl ether in the... 

Carbohydrate-derived titanium cnolates also provide yvn-x-amino-/l-hydroxy esters of high diastcrcomeric and enantiomeric purity. For this purpose, the lithium enolate derived from ethyl (2,2,5,5-tetramcthyl-2,5-disilapyrrolidin-l-yl)acetate is first transmctalated with chloro(cy-clopentadienyl)bis(1,2 5,6-di-0-isopropylidene-a-D-glucofuranos-3-0-yl)titanium and subsequently reacted with aldehydes.. vj-n-a-Amino-/ -hydroxy esters are almost exclusively obtained via a predominant /te-side attack (synjanti 92 8 to 96 4 87-98% ee for the xvn-adducts)623-b. 

In another approach, a glucose-derived titanium enolate is used in order to accomplish stereoselective aldol additions. Again the chiral information lies in the metallic portion of the enolate. Thus, the lithiated /m-butyl acetate is transmetalated with chloro(cyclopentadienyl)bis(l,2 5,6-di-0-isopropylidene- -D-glucofuranos-3-0-yl)titanium (see Section I.3.4.2.2.I. and 1.3.4.2.2.2.). The titanium enolate 5 is reacted in situ with aldehydes to provide, after hydrolysis, /i-hydroxy-carboxylic acids with 90 95% ee and the chiral auxiliary reagent can be recovered76. 

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