C-Tritylation

Treatment of benzyl 2-acetamido-3,4-anhydro-2-deoxy-6-C>-trityl-a-D-allopyranoside (412) with tetrabutylammonium fluoride [BU4NF in refluxing (refl.) MeCN, 24 h] gave, under diaxial ring-opening, benzyl 2-acetamido-2,4-dideoxy-4-fluoro-6-f9-trityl-a -D-gulopyranoside (413), in... 

After the deprotection of 0-xylenephosphate groups by catalytic hydrogenation in the presence of Pd-C (step c) trityl and acetyl groups were re-... 

Condensation with elimination of hydrogen halides C-Tritylation of ar. compounds... 

G Tritylation. A 1 6.5 mixture of trityl chloride and diphenylamine heated 0.5 hr. on a water bath -> 4-trityldiphenylamine. Y 79%.—Ar. sec. amines give C-trityl derivatives under conditions which yield N-trityl derivatives when applied to prim, amines. F. e. s. P. E. Verkade, H. van der Goot, and F. D. Tollenaar, R. 83, 696 (1964). 

Buchanan s group has published details of the reaction of 2,3-C-isopro-pylidene-D-ribofuranose with ethynylmagnesium bromide to yield 1,2-dideoxy-4,5-C-isopropylidene-D-a//o-hept-l-ynitol, which was converted into its 7-trityl ether. Treatment of this trityl ether with toluene-/7-sulphonyl chloride in pyridine furnished 2,3-0-isopropylidene-5-C-trityl-a-D-ribofuranosylethyne (35). 

Trityl Ethers. Treatment of sucrose with four molar equivalents of chlorotriphenylmethyl chloride (trityl chloride) in pyridine gives, after acetylation and chromatography, 6,1, 6 -tri-O-tritylsucrose [35674-14-7] and 6,6 -di-O-tritylsucrose [35674-15-8] in 50 and 30% yield, respectively (16). Conventional acetylation of 6,1, 6 -tri-O-tritylsucrose, followed by detritylation and concomitant C-4 to C-6 acetyl migration using aqueous acetic acid, yields a pentaacetate, which on chlorination using thionyl chloride in pyridine and deacetylation produces 4,l, 6 -trichloro-4,l, 6 -trideoxygalactosucrose [56038-13-2] (sucralose), alow calorie sweetener (17). 

The stereoselective introduction of two methyl groups into / -(- -)-5-hydroxy-methyl-2(5// )-furanone 143 was effected by tritylation followed by the conjugated addition (87JOC1170) of McaCuLi (TMSCl/EtaO, -78°C) and, finally, treatment with LiN(TMS)2/MeI (Scheme 43) (97TL1439). 

If the alkyl halide contains more than one, equally reactive C-halogen centers, these will generally react each with one aromatic substrate molecule. For example dichloromethane reacts with benzene to give diphenylmethane, and chloroform will give triphenylmethane. The reaction of tetrachloromethane with benzene however stops with the formation of triphenyl chloromethane 7 (trityl chloride), because further reaction is sterically hindered ... 

Several other methods for the introduction of halo atoms at C-6 in hexose derivatives have been known since the late 1920s. One of the earlier methods involved the reaction of methyl 2,3,4-tri-0-acetyl-6-0-trityl-a-D-glucopyranoside with phosphorus pentachloride which resulted only in an 8% overall yield of methyl 6-chloro-6-deoxy-a-D-glucoside (57). In contrast, the reaction of methyl 2,3,4-tri-0-acetyl-6-0-trityl-a-D-altropyranoside with phosphorus tribromide and bromine afforded a 73% yield of the corresponding 6-bromo-6-deoxy derivative (91). 

In subsequent studies,22 Sheehan et al. demonstrated that the action of diisopropylcarbodiimide on penicilloate 24, prepared by protection of the free primary amino group in 23 with trityl chloride (see Scheme 6b), results in the formation of the desired -lactam 25 in a very respectable yield of 67 %. In this most successful transformation, the competing azlactonization reaction is prevented by the use of a trityl group (Ph3C) to protect the C-6 amino function. Hydrogenolysis of the benzyl ester function in 25, followed by removal of the trityl protecting group with dilute aqueous HC1, furnishes 6-aminopenicillanic acid (26), a versatile intermediate for the synthesis of natural and unnatural penicillins. 

Although trityl perchlorate is used to accomplish the glycosidation of the C-8 hydroxyl in 44 with acetoxy glycoside 49, control experiments have demonstrated that no reaction takes place in the presence of 4 A molecular sieves or 2,6-di-terf-butylpyridine. This observation suggests that the actual catalyst is not trityl perchlorate, but perchloric acid. Consistent with this conclusion is the observation that catalytic amounts of a strong Brpnsted acid such as triflic or perchloric acid can catalyze the glycosidation of 44 with 49 in the absence of trityl perchlorate. 

Attempts to prepare 2-aminoazepinium cations by the action of trityl tetrafluoroborate on 3//-azepin-2-amines have failed,64 as have attempts to Ar-methylate 2,5,7-trimethyl-3/f-azepine with an excess of iodomcthanc in a scaled tube at 100°C for seven hours.77 In contrast, the unstable Ar,Ar-dialkyl-6-(methylsulfanyl)-3//-azepin-2-amines, e. g. 1, with trityl tetrafluoroborate, or the corresponding nitrosonium salts, yield their tetrafluoroborate salts, e.g. 2s4 (see also Section 3.1.1.5.4.). 

Draw stick structures to represent each of the following species (a) 2,2.3,3-tetramethylhexane, CH C(CH3),C(CH )2CH,CH2CH3 (b) the trityl cation, (C6Hj)3Ci (c) butadiene, CH2CHCHCH2. 

Giacomelli et al. constructed 3-propylisoxazole-5-yl-methanol via a [3-1-2] cycioaddition (Fig. 15) [158]. Nitrobutane was converted to nitrile oxide in the presence of 4-(4,6-dimethoxy [1,3,5]triazin-2-yl)-4-methylmorpholinium chloride (DMTMM) and catalytic 4-dimethylaminopyridine (DMAP). Trityl chloride resin-bound propargyl alcohol was employed as the dipolarophile to trap the nitrile oxide, forming the cyclo adduct isoxazole ring under unusually mild conditions (i.e., microwave irradiation at 80 °C for five times 1 min). Disappearance of the starting material was monitored by FT-IR. 

Bis(4-formylphenyl) succinate 2201 and octamethylene N,N -bis(trimethylsilyl) carbamate 2202 condense with aUyltrimethylsilane 82 in the presence of 10 mol% trityl perchlorate or TMSOTf 20 to give, after 24 h at 0°C in CH2CI2, the poly-... 

This problem can be suppressed by introducing a bulky steric group, such as the trityl-based resins (Fig. 8), at the C-terminal peptide-anchorage. 

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