Under conditions B, the mono-methylated product 16 is formed. What does the position of methylation tell you?

1. Under conditions C, the decomposition product 17 is formed. Why does the change in reaction conditions (relative to A) open this alternative pathway?
2. 

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Ph. O-g-Ar N. 14 H A i. 2 x CHILI, -78 C ii. DO B 1.2xCHL, -78C i. 1xCHy iii. HO (work-up) i. 2 x CHILI, 25 C ii. DO Ph. Ph. Ph. O-g-Ar N. N D 15 16 0-g-Ar N. N H 17 00 D D