Protection 2- ethyl chloroformate

The ethoxycarbonyl group was developed for the protection of phosphonates. The derivative is prepared by reaction of tris(trimethylsilyl) phosphite with ethyl chloroformate and can be cleaved by hydrolysis of the ester followed by silyla-tion with bistrimethylsilylacetamide. ... 

The synthesis of key intermediate 12, in optically active form, commences with the resolution of racemic trans-2,3-epoxybutyric acid (27), a substance readily obtained by epoxidation of crotonic acid (26) (see Scheme 5). Treatment of racemic 27 with enantio-merically pure (S)-(-)-1 -a-napthylethylamine affords a 1 1 mixture of diastereomeric ammonium salts which can be resolved by recrystallization from absolute ethanol. Acidification of the resolved diastereomeric ammonium salts with methanesulfonic acid and extraction furnishes both epoxy acid enantiomers in eantiomerically pure form. Because the optical rotation and absolute configuration of one of the antipodes was known, the identity of enantiomerically pure epoxy acid, (+)-27, with the absolute configuration required for a synthesis of erythronolide B, could be confirmed. Sequential treatment of (+)-27 with ethyl chloroformate, excess sodium boro-hydride, and 2-methoxypropene with a trace of phosphorous oxychloride affords protected intermediate 28 in an overall yield of 76%. The action of ethyl chloroformate on carboxylic acid (+)-27 affords a mixed carbonic anhydride which is subsequently reduced by sodium borohydride to a primary alcohol. Protection of the primary hydroxyl group in the form of a mixed ketal is achieved easily with 2-methoxypropene and a catalytic amount of phosphorous oxychloride. 

Diazomethane is generated by the reaction of aqueous NaOH with N-methyl-N-nitroso-p-toluenesulfonamide (Diazald ) in DMSO. The diazomethane is generated quantitatively and is removed by a stream of N2 into a packed column containing a stream of mixed anhydride formed from an N-protected (BOC or CBZ) amino acid and ethyl chloroformate. The diazoketone is converted to the chloroketone using HCI, as shown in Scheme 11.10. The chiral epoxide can then be formed via diastereoselective reduction with NaBH4 and treatment with base. 

The magnesium bromide salt of indole gives the 3-carboxy derivatives in about 30% yield on reaction with carbon dioxide (56JCS2853). Ethyl indole-3-carboxylate can be obtained directly, but in modest yield, using ethyl chloroformate (62JOC496, 6602805). Indole-2-carboxylic acid derivatives can be obtained via the benzenesulfonyl-protected 2-lithio derivative (equation 181) (73JOC3324). 

In addition to the preparation of a- and /3-hydrastine described above from the betaine (64), another conversion of a tetrahydroberberine into hydrastine has been reported. Acetylophiocarpine, on treatment with ethyl chloroformate, gives the acetoxy-derivative of (88), which can be hydrolysed to the hydroxymethyl compound and then oxidized to the aldehyde by pyridinium perchlorate. Hydrolysis of the acetoxyl group afforded the hemi-acetal (93 R = H), conversion of which into the mixed acetal (93 R = Et) protected the aldehyde system during reduction of N—C02Et to NMe by lithium aluminium hydride. Hydrolysis of the acetal, followed by oxidation, then gave a-hydrastine, and a similar sequence of reactions starting from O-acetyl-13-epi-ophiocarpine afforded / -hydrastine.119 Methods of synthesis of alkaloids of this group have been reviewed.120... 

The route used earlier338 in the partial synthesis of dihydro-epipleiocarpamine from dihydrocorynantheine has now been adapted to the synthesis of 16-epipleio-carpamine (134) from geissoschizine.80 The major modification required was the protection of the enolic hydroxy-group at C-17 in geissoschizine (92) by the formation of a carbonate ester with ethyl chloroformate following fission of the... 

The amino group in Z-Ala is protected as the nonnucleophilic amide half of a carbamate ester. The carboxyl group can be activated without reacting with the protected amino group. Treatment with ethyl chloroformate converts the carboxyl group to a mixed anhydride of the amino acid and carbonic acid. It is strongly activated toward nucleophilic attack. 

Summary DATB is prepared by reacting m-phenylenediamine with ethyl chloroformate to produce the urethane derivative. The urethane derivative is converted to the nitro derivative by treatment with 30% fuming sulfuric acid and 90% nitric acid. After which, heating with 98% sulfuric acid for three hours, reduces the nitro derivative of the urethane to DATB. Commercial Industrial note For related, or similar information, see Application No. 115,337, November 2, 1987, by Texas Explosives Co Inc, to David M. O Keefe, Mansfield, TX. Part or parts of this laboratory process may be protected by international, and/or commercial/industrial processes. Before using this process to legally manufacture the mentioned explosive, with intent to sell, consult any protected commercial or industrial processes related to, similar to, or additional to, the process discussed in this procedure. This process may be used to legally prepare the mentioned explosive for laboratory, educational, or research purposes. 

Acid-catalyzed addition of aliphatic, aromatic or heteroaromatic cyanohydrins to ethyl vinyl ether, n-butyl vinyl ether or dihydro-4//-pyran provides base stable, protected cyanohydrin derivatives. Phase transfer catalyzed alkylation of aliphatic cyanohydrins with allylic bromides gave a-substituted a-allyl-oxyacetonitrile. Carbonyl compounds react wiA cyanide under phase transfer catalysis to give cyanohydrin anions, which are trapped by an acyl chloride or ethyl chloroformate to give acyl- or alkoxycarbonyl-protected cyanohydrins respectively. The reduction of the carbonyl group of an acyl cyanide by NaBH4 under phase transfer conditions followed by esterification serves as an alternative route to aldehyde-derived cyanohydrin esters. ... 

Ethyl Chloroformate Air-line mask, self-contained breathing apparatus, or organic and canister mask full protective clothing. Remove patient to fresh air if breathing stops give artificial respiration. Call doctor, keep victim quiet and administer oxygen if needed. Wash liberally with water for at least 15 minutes, then apply dilute solution of sodium bicarbonate or commercially prepared neutralizer. Rush with water for at least 15 minutes see a doctor. 

Thus, chalcone (26), available via aldol condensation between the appropriate benzaldehyde and acetophenone, was transformed into the 1,3-diarylpropene (27) via a two-step sequence involving ethyl chloroformate and NaBH4, followed by protection of the phenolic hydroxy group as the TBDMS ether. Asymmetric dihydroxylation of olefin (2 7) with AD-mix-a gave an intermediate diol, which was converted into ortho-ester (28) with triethyl orthoformate in the presence of catalytic pyridinium -toluenesulfonate (PPTS), followed by deprotection of the TBDMS ether with TBAF in THE. Treatment of ortho-ester (28) with triethyl orthoformate and PPTS gave an intermediate (27( ,35)- w j -flavan-3-ol formate ester. De-esterification with K2CO3 in THF/methanol and oxidation of the... 

To a cold (—15°C) solution of iV-Fmoc- or Boc-protected a-amino acid (10 mmol) in 1,2-dimethoxyethane (10 mL) or THF (10 mL) are successively added NMM (1.11 mL, 10 mmol) and ethyl chloroformate (1.39 mL, 10 mmol). The reaction mixture is stirred at — 15°C for 1 min and the precipitated NMM-HCl is rapidly filtered. An aqueous solution (5 mL) of NaBH4 (570 mg, 15 mmol) is then added to the filtrate. After the evolution of gas is stopped, 250 mL of water is added at once. If the -amino alcohol precipitates, it is filtered, washed with water and hexane, and dried under high vacuum. Otherwise, it is extracted with AcOEt and the organic layer is... 

The synthesis of fragment B will be done according to Scheme 3. The known hexacarbonyldicobalt complexed alkyne (12) will be prepared according to the work done by Krafft and co workers. First, 3-butyn-l-ol (13) will be converted to its rerr-butyldimethylsilyl (TBS) ether by treating a mixture of (13) with TBS-Cl in triethylamine and DMAP. Treatment of the protected alkynol with 5ec-butyl lithium in THF followed by low temperature quench with ethyl chloroformate yields the alkynoate (14). The alkynoate is then complexed with dicobaltoctacarbonyl in petroleum ether to yield (12) in excellent yield. 

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