Syntheses of 2,5-dimethyl-4-naphth-2′-yldioxolanes and their stereoselective isomerization to naphtho[1,2-c]pyrans, angular analogues of glucoside B, a cleavage product of the aphid insect pigments the protoaphins

Giles, R.G.F. and Gruchlik, Y. (2004) Syntheses of 2,5-dimethyl-4-naphth-2′-yldioxolanes and their stereoselective isomerization to naphtho[1,2-c]pyrans, angular analogues of glucoside B, a cleavage product of the aphid insect pigments the protoaphins. Arkivoc, 10 . pp. 134-151.

Abstract

Benzynes were generated selectively through loss of ortho-bromotosylate from 1,2-dibromo-3- tosylates. Thus when treated with bu tyl lithium in the presence of furan rel -(2 R ,4 S ,5 R )-4-(2',3'- dibromo-5'-methoxy-4'-toluene- p -sulfonyloxyphenyl)-2,5-d imethyl-1,3-dioxolane 21 was converted in two steps into rel -(2 R ,4 S ,5 R )-4-(1'-bromo-4'-methoxynaphthalen-2'-yl)-2,5- dimethyl-1,3-dioxolane 8 in good yield. Attempted stereoselective isomerization of dioxolane 8 with titanium(IV) chloride at low temperature led to the recovery, almost exclusively, of starting material. The debrominated analogue rel -(2 R ,4 S ,5 R )-4-(1'-methoxynaphthalen-3'-yl)-2,5- dimethyl-1,3-dioxolane 31 , on the other hand, isomerized readily to give rel -(1 R ,3 R ,4 S )- and rel - (1 S ,3 R ,4 S )-3,4-dihydro-4-hydroxy-6-met hoxy-1,3-dimethylnaphtho[1,2- c ]pyrans 32 and 34 in a ratio (~1:3) that did not vary with reaction temperature.

Item Type:	Journal Article
Murdoch Affiliation(s):	School of Chemical and Mathematical Science
Publisher:	Michigan Publishing
Copyright:	© 2004 ARKAT USA, Inc
URI:	http://researchrepository.murdoch.edu.au/id/eprint/32990

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