Table 7.

Calculated [M06-2X/6-31+G(d,p)] NCIs, including distances, angles and contact type from the ZPE-corrected geometry of each of the endo TSs of the Diels–Alder reactions of dienes 8b, 8c, 8g, 8j and 18a with dienophiles 7b,c.^a

TS cycloaddends	interactionb	distance (Å)	angle (º)	contact typec
8b/7c	C–H···O	2.962	131.89	D–H···A
8b/7c	π···π	3.626	4.24	π-stacking (parallel-displaced)
8c/7c	C–H···O	2.741	119.78	D–H···A
8c/7c	C–H···Brd	3.289	98.02	D–H···A
8c/7c	π···π	3.684	16.02	π-stacking (parallel-displaced)
8g/7c	C–H···Oe	2.660	163.14	D–H···A
8g/7c	π···π	3.683	15.90	π-stacking (parallel-displaced)
8j/7c	Cethynyl–H···πf	2.530	115.19	D–H···A
8c/7b	Cmethyl–H···πg	2.537	126.61	D–H···A
8c/7b	C–H···Brh	2.771	160.54	D–H···A
18a/7c	Cmethylene–H···πi	2.429	154.71	D–H···A

^aData taken from the TS geometry, obtained from the relative zero-point corrected energy (Figure 4). ^bThe intermolecular C–H···O interaction derived from the proton of the benzene ring or the proton of the methoxy group of the ester of the diene and a carbonyl oxygen of the dienophile. ^cD = donating atom; A = acceptor atom or aromatic ring. ^dThe intermolecular C–H···Br derived from the aryl proton of 7c and the bromine atom of diene 8c. ^eThe intermolecular C–H···O interaction derived from the proton of the benzene ring of 7c and of the carbonyl oxygen of diene 8g. ^fThe C–H···π interaction derived from the proton of the terminal acetylene of diene 8j and the benzene ring of 7c. ^gThe C–H···π interaction derived from the proton of the N-methyl group of 7b and the benzene ring of 8c. ^hThe intramolecular C–H···Br interaction derived from the vinylic proton and the bromine atom of diene 8c. ⁱThe C–H···π interaction derived from the proton of methylene of the pyrrolizine moiety of diene 18a and the benzene ring of 7c.