5,10,15,20-Tetraphenylporphyrin chromium chloride (TPPCrCl) with added [Ph3P-N-PPh3]Cl+ (PPN+Cl) selectively polymerizes lactide (l and rac) dissolved in neat propylene oxide (PO) to yield polylactide (PLA) terminated by the -OCHMeCH2Cl group. At 0 degrees C and below, rac-LA yields polymers highly enriched in isotactic tetrads (iii). At 25 degrees C, some stereoselectivity is lost as transesterification becomes significant, and at 60 degrees C and above, enchainment of PO leads to the formation of 3,6-dimethyl-1,4-dioxan-2-one by a backbiting mechanism. At 0 degrees C, after the enchainment of l-(S,S)-LA in neat (R)-(+)-PO, the formation of (3S,6R)-3,6-dimethyl-1,4-dioxan-2-one occurs, while at higher temperatures the ratio of (3S,6R)-3,6-dimethyl-1,4-dioxan-2-one to (3R,6R)-3,6-dimethyl-1,4-dioxan-2-one falls to 3:2.