L-Naphthyl isocyanate

The cyclic carbamate (oxazolidin-2-one) 313 is formed by the reaction of phenyl isocyanate (312) with vinyloxirane[192]. Nitrogen serves as a nucleophile and attacks the carbon vicinal to the oxygen exclusively. The thermodynamically less stable Z-isomer 315 was obtained as a major product (10 1) by the reaction of 2-methoxy-l-naphthyl isocyanate (314) with a vinyloxir-... 

If 2-methoxy-l-naphthyl isocyanate is used, the N-aryloxazolidinone can be cleaved by CAN to furnish the corresponding N-unsubstituted oxazolidinone in 70-85% yield. 

To a yellow solution of the catalyst prepared by simply stirring 25.0 mg (0.12 mmol) of triisopropyl phosphite with 10.4mg (0.01 mmol) of Pd,(dba)3 CHC13 in 0.5-1.OmL of THF are added 2l9mg (1.1 mmol) of 2-methoxy-l-naphthyl isocyanate. 1 mmol of the epoxide 17a-g is added in one portion, either neat or dissolved in 1 mL of THF, and the resultant mixture is stirred at r.t. for 12—24 h until conversion is complete. Evaporation of the solvent in vacuo and flash chromatography affords the pure 2-oxazolidinones 18 a-g in the yields given in Table 7. 

From theGrignard reagent (prepared from the alkyl halide and magnesium m dry ether) with l-naphthyl-isocyanate in ether... 

Naphthol is mainly used in the manufacture of the insecticide carbaryl (59), l-naphthyl A/-methyicarbamate/ iJ-2j5 - (Sevin) (22), which is produced by the reaction of 1-naphthol with methyl isocyanate. Methyl isocyanate is usually prepared by treating methylamine with phosgene. Methyl isocyanate is a very toxic Hquid, boiling at 38°C, and should not be stored for long periods of time (Bhopal accident, India). India has developed a process for the preparation of aryl esters of A/-alkyl carbamic acids. Thus l-naphthyl methylcarbamate is prepared by refluxing 1-naphthol with ethyl methylcarbamate and POCl in toluene (60). In 1992, carbaryl production totaled > 11.4 x 10 t(35). Rhc ne-Poulenc, at its Institute, W. Va., facihty is the only carbaryl producer in United States. 

According to the submitters l-cyano-S-a-naphthylurea is obtained similarly from a-naphthyl isocyanate in 85-90% yields. Crystallization from acetone-petroleum ether (12 and 6 ml., respectively, per gram of crude product recovery approximately 60% per crystallization) yields lustrous prisms, m.p. 148-149 with decomposition. 

Reaction of a-naphthyl isocyanate and hydrazides to yield l-acyl-4-arylsemicarbazides [90]. 

Resolution of alcohols (cf., l-(naphthyl)cthyl isocyanate, 8, 356 357). A practical synthesis of the methyl ester of (S)-5-HF,TF. (1) from arachidonic acid involves chromatographic separation of the diastereomeric urethanes preparecT from the Isocyanate derived from dehydroabietylamine (hydrogen chloride and phosgene).1 Urethanes from other chiral amines are less useful. The urethanes are cleaved with triethylamine and trichlorosilanc to give the corresponding pure enantiomeric esters, which can be hydrolyzed by base. 

Resolution of sec-amines. Reaction of sec-amines with (+)- or (- )-l results in two diasteriomeric ureas, R2NCONH(CH3)C6H5, which can usually be resolved by either chromatography or crystallization. The resolved sec-amine is obtained by alcoholysis of the optically pure urea. The method is particularly valuable where both optical isomers of the amine are desired see also (R)-( - )-(l-naphthyl)ethyl isocyanate (6, 416) for a similar reagent. 

Symmetrically substituted carbodiimides are also obtained from iminophosphoranes and carbon dioxide or carbon disulfide, involving isocyanates or isothiocyanates as intermediates. Instead of the heterocumulenes di-t-butylcarbonate is also used in the reaction with iminophosphoranes. For example, bis(l-naphthyl)carbodiimide is obtained in 64 % yield using this procedure. 

Analysis of Reagent Purity diastereomeric purity can be assessed by the H NMR chemical shift of the methyl groups, and by GC analysis. Optical purity can be assessed by derivatiza-tion with (/ )-(—)-l-(l-naphthyl)ethyl isocyanate and H NMR analysis of the product. ... 

Chiral alcohols are smoothly transformed to the corresponding (f )-[l-(l-naphthyl) ethyljcarbamates by treating with (f )-l-(-naphthyl)ethyl isocyanates in the presence of distannoxane catalyst (Eq. 103) [146],... 

More readily carbamoylation of 1-morpholinocyclohexene with 1-naphthyl isocyanate gave a mixture of isomeric 2-morpholino-A -(l-naphthyl)cyclohex-l(or2)-ene-l-carboxamide in 85% yield. Successive treatment with 7V-chlorosuccinimide (NCS) in acetonitrile gave 3-chloro-2-morpholino-iV-(l-naphthyl)cyclohex-l-ene-l-carboxamide (21) in 74% yield. 

Combination of a nonracemic isocyanate and a l,3-disul)sliluted distannoxane has provided a new method for determination of the optical purity of chiral alcohols (Scheme 12.174) [316]. When a chiral alcohol was reacted with commercially available (l )-l-(l-naphthyl)efhyl isocyanate in the presence of 1,3-disubstituted distannoxane, formation of the desired carbamates occurred rapidly, with acid-labile functional groups such as ester, THP and /Miydroxyketone remaining intact. Subsequent HPLC analysis of the resulting carbamate revealed a pair of well-separated peaks of diastereomers derived from both enantiomeric alcohols. 

Dehydration of keto diol ( )-A derived from geraniol furnished furanone ( )-B. Its reduction with sodium borohydride yielded alcohol ( )-C as the major product. Treatment of ( )-C with the isocyanate derived from (/ )-l-(l-naphthyl)ethylamine gave a mixture of carbamates E and F. These were separable by medium-pressure liquid chromatography (MPLC), and E gave (+)-C, while F afforded (—)-C. 

The mercury(II)-catalyzed equilibration of diastereomeric carbamates 3b, prepared from methyl m-l-(l-naphthyl)ethyl isocyanate, leads to a mixture of 3b and 4b. Separation of 4b, followed by repetitive equilibration of the unwanted 3 b, provides a new method for transferring racemic allylic alcohols into a single enantiomer431. Alcohol 4c was used in the synthesis of enantiomerically pure prostanoids. 

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