Alkoxy and aryloxy groups

8 Other 0-Linked Substituents 3.2.3.8.1 Alkoxy and aryloxy groups 

Aryloxy groups are more resistant to rearrangement (unless nitro-activation of the aryl group is present) however, under forcing conditions the reaction (843 — 844) forms the basis for a synthetic technique for converting a phenol into an amine. 

---

Alkyl-substituted pyridines have been complexed with a wide variety of other boron Lewis acids, BH3, B(OH)3, and BX3, where X is a selection of alkyl, aryl, hydroxy, alkoxy, and aryloxy groups <87JCS(P2)77l). 

Replacement of Fluorine by Alkoxy and Aryloxy Groups 4.2.1. In Aliphatic Compounds... 

Examples of replacement of fluorine in saturated aliphatic perfluorinated compounds by alkoxy and aryloxy groups are relatively scarce since such fluorine atoms are generally inert toward nucleophiles in SN2 reactions. 

However, replacement of alkoxy and aryloxy groups from phosphorus hahdes by Grignard reagents is reported to be facile in the early literature (116). Undoubtedly, low temperature, tetrahydrofuran as a solvent, and the inverse-addition sequence might be anticipated to improve yields of the phosphinates. 

Exchange reactions are common between boron halides and alkyl or aryl substituents, other halides, alkoxy and aryloxy groups, and diborane. Some examples are shown in Scheme 2. 

Alkoxy and aryloxy groups bonded to silicon are first acetylated with acetic anhydride, using perchloric acid as catalyst, in an ethyl acetate solvent. Following... 

Substitution of fluorine by alkoxy and aryloxy groups occurs especially easily (Scheme 12). Thus, 4-(l-naphthoxy)trifluorophthalonitrile was obtained upon treatment of TFPN with equimolar amount of sodium 1-naphtolate in methanol at room temperature (71 %) [26], Reaction of TFPN with 1-adamantanol (1 2 ratio) in the presence of BuLi in THF affords 4,5-diadamantyloxy substituted dinitrile (RT, 76 %) [27], All fluorine atoms are substituted when TFPN is heated with alcohols or phenols in DMF in the presence of K2CO3 as a base [27-29], In such way, among others tetrakis(2,2,2-trifluoroethoxy)- and tetrakis(2,2,3,3,3-pentafluoropropoxy) phthalodinitriles 50a and 50b (yields >90 %) - the precursors for the fluorine-coated phthalocyanines were obtained [28, 29]. 

Scheme 40 Synthesis of porphyrazines with perfluorinated alkoxy and aryloxy groups...

As well as alkoxy- and aryloxy-groups, the corresponding sulphur functions have been replaced in the amination of pyridine l-oxides s and quaternary pyridinium salts Examples with pyridines are rare" . An interesting intramolecular amination occurs in the transformation of 2-pyridyl-2 -(3 -aminopyridyl)thioether into 3-(2 -pyridylamino)pyridine-2-thiol 09 l-Alkylpyrid-2>thiones, warmed with alcoholic ammonia and mercuric oxide, give l-alkylpyrid-2-one-imines ii. 

---