Table 1.

Conditions optimization.

Entry	L	x(%)/y(%)	temp/time	additive	conversion	2a/2a’b
1c	L1	5/10	80 °C/15 h	-	7%	-
2	L1	5/10	80 °C/15 h	-	76%	<2%/23%
3	L2	5/10	80 °C/15 h	-	21%	-
4	L3	5/10	80 °C/15 h	-	20%	<2%/8%
5	L4	5/10	80 °C/15 h	-	54%	18%/35%
6	PPh3	5/10	80 °C/15 h	-	20%	-
7	Johnphos	5/10	80 °C/15 h	-	20%	-
8	WangPhos	5/10	80 °C/15 h	-	20%	-
9	L4	5/10	80 °C/15 h	3Å MS	25%	-
10	L4	5/10	80 °C/15 h	Boc2Od	100%	72%/26%
11e	L4	5/10	80 °C/15 h	Boc2Od	100%	73%/26%
12	L4	5/10	80 °C/30 h	Boc2Od	100%	91%f/0%

^aAll the reactions were run in DCE (0.05 M) in sealed vials.

^bNMR yield using triisopropylbenzene as the internal reference.

^cNo N-phenylmaleiimide was added.

^d2 equiv. used.

^eReaction run under Ar.

^f86% isolated yield.