Non-nucleoside reverse transcriptase inhibitors

A compound according to formula I wherein:

• A is
• (a) CHR3═CHR2,
• (b) CH2R3CH2R2, or,
• (c) CHR2;
• either (i) R1 is II and R2 is hydrogen, C1-3 alkyl, C1-3 haloalkyl, C2-6 alkenyl, or CH2ORc;
• and, in addition, if A is either (a) or (b) R2 can also be halogen, NRaRb, CN, or ORc;
• or, (ii) R1 is C1-6 alkyl and R2 is II;
• X1 is O or S;
• X2 is O, or, if A is (a), X2 is O or NRd;
• R3 is hydrogen or C1-3 alkyl;
• R4 is halogen, C1-6 alkyl, C3-6 cycloalkyl C1-6 haloalkyl or C1-6 alkoxy;
• Ra and Rb are independently hydrogen, C1-3 alkyl or C1-6 acyl;
• Rc and Rd are independently hydrogen or C1-3 alkyl;
• Ar is phenyl substituted with 1 to 3 groups independently selected from halogen, cyano, C1-6 haloalkyl, C1-6 alkyl, C1-6 alkoxy or C3-6 cycloalkyl;
• n is an integer from 1 to 3;
• or,
• pharmaceutically acceptable salts thereof.