Ethyl-2-naphthoate

The synthetic utility of the ring expansion reaction was demonstrated by its application to the synthesis of thermolabile thiepins. When the diazo compound (66) obtained from benzo[c]thiopyrylium salt 65 was treated with palladium catalyst under the same conditions as in the case of 63, the product isolated was ethyl 2-naphthoate (68)48). The plausible reaction pathway is one comprising i) decomposition of 66 to the corresponding carbene intermediate, ii) ring expansion to the... 

Methyl 1-naphthoate Ethyl 1-naphthoate Ethyl 2-naphthoate Methyl 2-naphthoate... 

Schulman and co-workers have invoked non-fluorescent H30 + exciplexes to interpret similar breaks in the titration curves of 1- and 2-ethyl naphthoate (Kovi and Schulman, 1972), 1-naphthoic acid and methyl-l-naphthylketone (Capomacchia et al., 1973). It is difficult to explain why in some cases only the 1-isomer shows this behaviour. It has also been suggested (Capomacchia et al., 1973) that the fluorescence titration curve reported by Watkins (1972b) for 2-naphthamide is an example of the same phenomenon although the B and BH+ curves seem to be complementary at lower acidities in this case (see Fig. 4). 

The rate of saponification of ethyl 2-thenoate, in contrast to ethyl 3-thenoate, was found to be considerably slower than predicted from the pKa of the acid, showing that the reactivities of thiophenes do not parallel those of benzene. The first explanation, that this was produced by a steric effect of the ring sulfur similar to the case in or /lo-substituted benzenes and in ethyl 1-naphthoate, could not be upheld when the same effect was found in ethyl 2-furoate. It was later ascribed to a stereospecific acid strengthening factor, involving the proper relation of the carboxylic hydrogen and the heteroatom, as the rate of saponification of 2-thienylacrylic acid was in agreement with that predicted from the acid constants. ... 

In situ iithiodibromomethane preparation/addition. An oven-dried, 2-L, round-bottomed flask with three vertical necks, containing 20.0 g (0.100 mol) of ethyl 1-naphthoate (Note 4), is equipped with a 2-1/2 x 3/4-inch, egg-shaped magnetic stirring bar (Note 5), a -100°C to +50°C thermometer (Note 6) and a rubber septum. 

Two modifications were made to our general procedure,43 specifically to suit the ethyl 1-naphthoate case in this preparation, that are not necessary for most other... 

The lithium tetramethylpiperidide solution from Part A is cooled with a dry ice-acetone bath. When the solution of ethyl 1-naphthoate and dibromomethane has cooled to -74°C or below (internal solution temperature), addition of the dry ice-acetone cooled solution of lithium tetramethylpiperidide is begun. Addition is made via a double-ended (16 gauge) needle over a 40 to 50-min period using a slight positive nitrogen pressure in the 500-mL flask (Note 7). During this time, the addition rate is slowed or stopped as needed to maintain the reaction temperature below -67 C. 

Ethyl 1-naphthoate was purchased from Lancaster Synthesis, Inc., P.O. Box 1000, Windham, NH 03087, and used without purification. The checkers found that the purity of the ester was 95% by capillary GC analysis. 

The current procedure starts with the ester, ethyl 1-naphthoate, and converts it into homologated product in 81% yield without isolation of any intermediates. Safe, commercially available materials are employed. Based on a recently published variation43 of our original homologation methods,4 1 It represents a general procedure applicable to esters 1 bearing aryl, alkenyl, alkynyl and primary, secondary or tertiary alkyl attachments R. Yields range from 67-90% (on a 25-mmol scale) and like the Arndt-Eistert sequence this procedure affords retention of stereochemistry for the... 

Ethyl 1-naphthoate 1-Naphthoic acid, ethyl ester (8) 1-Naphthalenecarboxylic acid, ethyl ester (9) (3007-97-4)... 

B. Ethyl l,3-dihydroxy-2-naphthoate. In a 1-1. flask 1 volume (87 ml.) of the crude ester is added in one lot to 3 volumes (261 ml.) of concentrated sulfuric acid without cooling, and the solution is allowed to stand for about 1 week (Note 4). The whole mixture, including any precipitate which may have formed, is poured slowly with stirring into a mixture of 1 kg. of icc and 500 ml. of water (Note 5) the solid yellow ester is filtered with suction, washed with a small amount of cold water, pressed in the filter for 30 minutes with a rubber dam, and finally dried in a vacuum desiccator. The yield of ester melting at 80° is 58-68 g. (50-59%, based on the malonic ester used). 

The yield of ethyl l,3-dihydroxy-2-naphthoate is decreased to 45% if the sulfuric acid solution is allowed to stand for only 2 days. 

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