Table 1.

Studies on the intramolecular Friedel-Crafts acylation.

Entry	Substrate	T [°C][a]	Selectivity [21 : 22][b]	Yield [%][c] of 21	Yield [%][c] of 22
1	20a (R = Ac)[d]	80	10 : 1	89	8
2	20b (R = C(O)(CH2)3N3)[d]	23	4 : 1	58	15
3	20b [d]	50	>20 : 1	81	-
4	20b	80	>20 : 1	84	-
5	20c (R = Boc)[e]	80	>20 : 1	72[f]	-

^[a]TFAA was added to the reaction mixture at the indicated temperature.

^[b]Selectivity was measured by crude ¹H NMR analysis.

^[c]Yields are based on isolation from silica gel column chromatography.

^[d]The crude reaction mixture was further treated with TFA for complete MOM deprotection.

^[e]Treatment with pyridine^[24] in EtOH was required to deprotect trifluroacetylated intermediates.

^[f]Boc group was cleaved during reactions: R = H. TFAA = trifluoroacetic anhydride, TFA = trifluoroacetic acid.